gitlab.rb should be before package

[LongLiveCHIEF]

Opened from: #165 (comment)

/etc/gitlab/gitlab.rb should be created/modified prior to installing the gitlab omnibus package reasons:

Fresh Install

The post-install steps of the gitlab omnibus package is designed to run gitlab-ctl reconfigure by default. If it does not detect a valid external_url in the file, it will skip this step, and reconfigure will have to be run manually. On a normal fresh install, the gitlab package will lay down the gitlab.rb.template, and will not identify a valid url, so it will skip this step. So far, this module has taken care of this by then laying down the desired changes to gitlab.rb, and notifying an Exec that runs reconfigure.

This then leaves the package able to identify a valid external_url, during post-install steps for upgrades, which means...

updates
As stated above, gitlab-ctl reconfigure runs by default when a valid external_url is identified. This means that if you add any configuration changes during a package update, then currently;

1. the install manifest will upgrade the package, running gitlab-ctl reconfigure
2. the config manifest will change the gitlab.rb and notify Exec['gitlab_reconfigure' (running reconfigure)
3. the service will restart, forcing gitlab offline, even if it was not necessary to do so.

With new HA features, this means we can't control the auto-reconfigure that will happen, because even though the post-install reconfigure will be skipped, the second (manual) execution of will run it anyways. This makes it difficult/impossible to separate the execution of gitlab-ctl reconfigure on a deploy node from the scenario when you are updating the package, vs actually changing the config.