Enhancement: Chef should check that the gitlab registry url won't listen on port 5000

Summary

I've started fiddling around with the new registry and, not thinking about it, gave it the same port as I'm used from our own registry. So my gitlab.rg file had something like: registry_external_url 'https://mydomain:5000' After gitlab-ctl reconfigure this resulted in gitlab either trying to restart nginx or the registry all the time, depending on which service got up faster.

Steps to reproduce

1. Add a registry_url with the same port the docker registry uses: registry_external_url 'https://mydomain:5000'

2. Reconfigure gitlab gitlab-ctl reconfigure

3. Profit

Expected behavior

It would be nice if gitlab would have told me my misconfiguration in the gitlab-ctl reconfigure step.

PS: Thanks for the hard work =)