Bug redis socket with auth

Originally started in https://gitlab.com/gitlab-org/gitlab-ce/issues/41530

Currently, Omnibus will not set GitLab to use a Redis password if it is using a unix socket.

This patch fixes that issue. It will add the password even if the Redis connection is using host/port, but this doesn't cause issues. I have not written any tests yet because I can't seem to clone the repository now - I made these changes on the web.

I searched the rest of omnibus for other places where this might be an issue:

• gitlab-workhorse.rb already has this change.
• gitlab-monitor.rb may have the same issue, but I can't test.