gitlab:check after nginx

You get the following error if you do `sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production` before nginx is installed/running:

```
Running /home/git/gitlab-shell/bin/check
Check GitLab API access: /usr/local/lib/ruby/2.0.0/net/http.rb:878:in `initialize': Connection refused - connect(2) (Errno::ECONNREFUSED)
    from /usr/local/lib/ruby/2.0.0/net/http.rb:878:in `open'
    from /usr/local/lib/ruby/2.0.0/net/http.rb:878:in `block in connect'
    from /usr/local/lib/ruby/2.0.0/timeout.rb:52:in `timeout'
    from /usr/local/lib/ruby/2.0.0/net/http.rb:877:in `connect'
    from /usr/local/lib/ruby/2.0.0/net/http.rb:862:in `do_start'
    from /usr/local/lib/ruby/2.0.0/net/http.rb:851:in `start'
    from /home/git/gitlab-shell/lib/gitlab_net.rb:62:in `get'
    from /home/git/gitlab-shell/lib/gitlab_net.rb:29:in `check'
    from /home/git/gitlab-shell/bin/check:11:in `<main>'
gitlab-shell self-check failed
  Try fixing it:
  Make sure GitLab is running;
  Check the gitlab-shell configuration file:
  sudo -u git -H editor /home/git/gitlab-shell/config.yml
  Please fix the error above and rerun the checks.
```

Should we be doing gitlab:check after nginx steps?