CI runner checks are too infrequent
### Summary
I am running gitlab-runner for projects on gitlab.com and it takes way too long between checks for new jobs
### Steps to reproduce
Excellent question.
* Create a project on gitlab.com.
* Run a runner for it on your own system (mine is installed on macOS via brew).
* Make a trivial pipeline
* Observe it takes several minutes from when you push changes to when the runner starts building them
### What is the current *bug* behavior?
Several minutes between runner checks
### What is the expected *correct* behavior?
A few seconds between runner checks
### Relevant logs and/or screenshots
```
# ps -ajxwww | grep gitlab-runner
1 1402 1402 1402 ? -1 Ssl 0 0:06 /usr/lib/gitlab-runner/gitlab-runner run --working-directory /home/gitlab-runner --config /etc/gitlab-runner/config.toml --service gitlab-runner --syslog --user gitlab-runner
```
```
# grep interval /etc/gitlab-runner/config.toml
check_interval = 10
```
```
# grep "Checking for jobs" /var/log/syslog
Aug 29 03:09:27 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:09:27 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:14:55 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:14:55 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:19:34 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:19:34 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:24:40 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:24:40 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:30:32 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:30:32 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:36:49 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
Aug 29 03:36:49 gitlab-ci-dispatch gitlab-runner[1402]: Checking for jobs... received
```
Note the 5+ minute intervals between checks even though check_interval is set to 10s (and I have multiple workers configured, so it should be even shorter than that).
### Output of checks
This bug happens on GitLab.com
issue