- Run the SELinux helper after GitLab Workhorse and other files are
  created ensuring their file contexts are restored
- Place GitLab Workhorse socket files into a sockets directory allowing
  the SELinux file context to be inherited on service restarts
- Add a GitLab Workhorse helper to ensure that new UNIX sockets for
  Workhorse always inherit the proper SELinux file context

Signed-off-by: Robert Marshall <rmarshall@gitlab.com>