Removal of gitlab.socket should be in stop function too. Fix #4313
Created by: axilleas
As @wojdec suggested in #4313 (closed), this fix first checks if gitlab.socket doesn't exist and iff the check returns a non-zero status (which means it exists), it then removes it.
I also removed the & in the restart function as I experienced some weird behaviour when I restarted the service (sidekiq didn't start after it stopped).
Tested on Debian 7.0, GitLab version 5.3.0.beta1.