Make it easier to use TCP sockets between Workhorse and Rails

Right now most communication between Rails and Unicorn happens over gitlab.socket. Unfortunately, this means it's not possible to use Wireshark to record the communication for debugging.

To get around this, I do this:

1. Tweak the gitlab-workhorse Procfile to use -authBackend http://127.0.0.1:8080 instead of -authSocket /Users/stanhu/gitlab/gdk-ee/gitlab.socket
2. Run thin via: bundle exec rake thin -p 8080

I tried to make Puma work by adding bind 'tcp://localhost:8080' to config/puma.rb but that didn't work for some reason. Seems to work fine.

I think it'd be nice to set a flag in the config to use TCP sockets instead of UNIX domain sockets so this could be done easily.