Remove unnecessary log alias for logrus inport

Some time ago [we had a discussion](!934 (comment 91891281))
about why we're aliasing some of the imports of `github.com/sirupsen/logrus`
package with a `log` alias.

At that moment we've been doing that in 17 from 68 cases when logrus
was imported in Runners codebase.

The conclusion was this aliasing is unnecessary, because:
- we relay on logrus interface so much that moving to another logging
  library will be not so simple as switching the import name;
- we're totally not consistent in the alias usage which makes the code
  even more messy.

Three GitLab Runner maintainers agreeded hat there is no reason to use
the aliasing and that we should just use `logrus` everywhere.

But no action was don since then. The cleanup was left for a future.

Unfortunately, because GitLab Runner is one of our biggest projects in
Go, for some people it becomes a source of suggestions of how certain
things should be handled. For example here is a discussion in a new
project that creates a go-based tool for our Serverless integration:

gitlabktl!9 (comment 152472275)

The most important statement is:

> perhaps we could leave it as is since it is how we are exposing
  logrus in the runner project

Because we already know that it should be changed and others start to
look on Runner's code to find good patterns, let's finally cleanup
the `log` aliasing mess.
39 jobs for remove-alias-for-logrus-imports in 50 minutes and 23 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Prebuild
passed #182102235
clone test repo

00:01:23

passed #182102238
dep check

00:01:37

passed #182102234
docker
helper images

00:06:03

manual #182102236
allowed to fail manual
review-docs-deploy
passed #182102237
gitlab-org
tests definitions

00:02:06

 
  Test
passed #182102239
code_quality

00:01:01

passed #182102252
docs check links

00:00:45

passed #182102261
git 1.7.1

00:02:20

passed #182102240
docker
unit test 1/5

00:09:48

passed #182102241
docker
unit test 2/5

00:15:46

passed #182102242
docker
unit test 3/5

00:10:38

passed #182102243
docker
unit test 4/5

00:04:06

passed #182102244
docker
unit test 5/5

00:02:59

passed #182102245
docker allowed to fail
unit test with race 1/5

00:11:27

failed #182102246
docker allowed to fail
unit test with race 2/5

00:17:44

passed #182102247
docker allowed to fail
unit test with race 3/5

00:13:58

passed #182102248
docker allowed to fail
unit test with race 4/5

00:04:57

failed #182102250
docker allowed to fail
unit test with race 5/5

00:08:16

failed #182102253
windows-1803 shell allowed to fail
windows 1803 tests 1/3

00:20:37

failed #182102254
windows-1803 shell allowed to fail
windows 1803 tests 2/3

00:34:14

failed #182102255
windows-1803 shell allowed to fail
windows 1803 tests 3/3

00:11:53

failed #182102257
windows-1809 shell allowed to fail
windows 1809 tests 1/3

00:17:18

failed #182102259
windows-1809 shell allowed to fail
windows 1809 tests 2/3

00:30:59

failed #182102260
windows-1809 shell allowed to fail
windows 1809 tests 3/3

00:08:52

 
  Coverage
passed #182102263
race conditions detector

00:01:02

passed #182102262
test coverage report

00:01:04

56.7%
passed #182102264
test junit report

00:01:24

 
  Build
passed #182102265
gitlab-org
binaries darwin/386 darwin/amd64

00:01:51

passed #182102266
gitlab-org
binaries freebsd/386 freebsd/amd64 freebsd/arm

00:02:12

passed #182102267
gitlab-org
binaries linux/386 linux/amd64 linux/arm

00:02:13

passed #182102268
gitlab-org
binaries windows/386 windows/amd64

00:01:59

 
  Package
passed #182102269
gitlab-org
package-deb

00:02:18

passed #182102270
gitlab-org
package-rpm

00:02:25

 
  Release
passed #182102271
release
development S3

00:01:11

passed #182102273
docker
development docker images

00:02:52

passed #182102274
windows-1803 shell
development nanoserver1803 helper docker image

00:03:58

passed #182102275
windows-1809 shell
development nanoserver1809 helper docker image

00:02:14

passed #182102276
static QA

00:00:38

 
  Cleanup
manual #182102278
allowed to fail manual
review-docs-cleanup
 
Name Stage Failure
failed
windows 1803 tests 2/3 Test
gitlab.com/gitlab-org/gitlab-runner/executors/shell-1

gitlab.com/gitlab-org/gitlab-runner/executors/shell-2
gitlab.com/gitlab-org/gitlab-runner/helpers/archives-0
gitlab.com/gitlab-org/gitlab-runner/helpers/archives-1


Running after script...
$ if (Test-Path $PKG_BUILD_DIR) { $(Get-Item $PKG_BUILD_DIR).Delete() }
ERROR: Job failed: exit status 1
failed
windows 1803 tests 3/3 Test
ok  	gitlab.com/gitlab-org/gitlab-runner/shells	6.486s

WARNING: Failed packages:
WARNING: gitlab.com/gitlab-org/gitlab-runner/helpers/docker-0


Running after script...
$ if (Test-Path $PKG_BUILD_DIR) { $(Get-Item $PKG_BUILD_DIR).Delete() }
ERROR: Job failed: exit status 1
failed
windows 1809 tests 2/3 Test
gitlab.com/gitlab-org/gitlab-runner/executors/shell-1

gitlab.com/gitlab-org/gitlab-runner/executors/shell-2
gitlab.com/gitlab-org/gitlab-runner/helpers/archives-0
gitlab.com/gitlab-org/gitlab-runner/helpers/archives-1


Running after script...
$ if (Test-Path $PKG_BUILD_DIR) { $(Get-Item $PKG_BUILD_DIR).Delete() }
ERROR: Job failed: exit status 1
failed
windows 1809 tests 3/3 Test
ok  	gitlab.com/gitlab-org/gitlab-runner/shells	6.767s

WARNING: Failed packages:
WARNING: gitlab.com/gitlab-org/gitlab-runner/helpers/docker-0


Running after script...
$ if (Test-Path $PKG_BUILD_DIR) { $(Get-Item $PKG_BUILD_DIR).Delete() }
ERROR: Job failed: exit status 1
failed
windows 1809 tests 1/3 Test

WARNING: Failed packages:
WARNING: gitlab.com/gitlab-org/gitlab-runner/executors/docker-2
gitlab.com/gitlab-org/gitlab-runner/executors/docker-4


Running after script...
$ if (Test-Path $PKG_BUILD_DIR) { $(Get-Item $PKG_BUILD_DIR).Delete() }
ERROR: Job failed: exit status 1
failed
unit test with race 5/5 Test
coverage: 6.9% of statements
ok gitlab.com/gitlab-org/gitlab-runner/shells 1.097s
Makefile:134: recipe for target 'parallel_test_execute' failed
make: *** [parallel_test_execute] Error 1
Uploading artifacts...
.cover/*: found 8 matching files
.testoutput/*: found 8 matching files
Uploading artifacts to coordinator... ok id=182102250 responseStatus=201 Created token=CzUSeEb1
ERROR: Job failed: exit code 1
failed
unit test with race 2/5 Test
exit status 1
FAIL gitlab.com/gitlab-org/gitlab-runner/executors/docker/machine 0.180s
Makefile:134: recipe for target 'parallel_test_execute' failed
make: *** [parallel_test_execute] Error 1
Uploading artifacts...
.cover/*: found 12 matching files
.testoutput/*: found 12 matching files
Uploading artifacts to coordinator... ok id=182102246 responseStatus=201 Created token=UFBC4qHm
ERROR: Job failed: exit code 1
failed
windows 1803 tests 1/3 Test

WARNING: Failed packages:
WARNING: gitlab.com/gitlab-org/gitlab-runner/executors/docker-2
gitlab.com/gitlab-org/gitlab-runner/executors/docker-4


Running after script...
$ if (Test-Path $PKG_BUILD_DIR) { $(Get-Item $PKG_BUILD_DIR).Delete() }
ERROR: Job failed: exit status 1