Fix multiple provisions

Before this PR the gitlab/gitlab-ci installation and database setup routines were executed with every Chef run, leading to the funny effect hat all projects, users, etc. were gone (drop database).

This PR adds `not_if` guards to make the `execute` resources idempotent. It also removes the `info_gitlabhq` resource which does not print anything to the screen during the Chef run, and it's for debugging only.

Finally this makes the converge time much faster.