Runner is still locked using the "--locked false" option when registering
## Summary
Runner is still locked when using the `--locked false` option with the `register` command. The Runner registers just fine but I then need to go into the GUI and unlock the runner.
However, If I use the environment variable `REGISTER_LOCKED=false` everything works as expected.
We only noticed this was an issue after default was set to [true][1] a few months ago.
## Steps to reproduce
```
gitlab-runner register -n \
-u https://example.com/ci \
-r xxxxxxxxxxxxx \
--name xxxxxxxxx \
--tag-list "xxxxxxxxx" \
--executor "docker" \
--output-limit "40960" \
--docker-privileged \
--docker-image docker:latest \
--docker-volumes /var/run/docker.sock:/var/run/docker.sock:rw \
--cache-type s3 \
--cache-s3-server-address "s3.amazonaws.com" \
--cache-s3-access-key XXXXXXXXXXXXXXX \
--cache-s3-secret-key XXXXXXXXXXXXXXX \
--cache-s3-bucket-name XXXXXXXXXXXXXX \
--cache-s3-bucket-location XXXXXXXXXX \
--cache-cache-shared true \
--locked false
```
## Actual behavior
Registers the runner locked.
## Expected behavior
Registers runner unlocked.
## Environment description
I have replicated this issue with the docker executor and the kubernetes executor as well.
### Used GitLab Runner version
gitlab-runner --version
Version: 10.4.0~beta.274.gd4dccf60
Git revision: d4dccf60
Git branch: cache_cap
GO version: go1.7.1
Built: Mon, 01 Jan 0001 00:00:00 +0000
OS/Arch: darwin/amd64
[1]: https://gitlab.com/45cali/gitlab-ci-multi-runner/commit/1a3497bb066cbab5aed61fa7d972994122dd3bcf
issue