Merge pull request #6782 from pkgr/allow-to-change-gitlab-config-location-via-env-variable

Allow to overwrite location of gitlab.yml config file.

config/initializers/1_settings.rb

 class Settings < Settingslogic
-  source "#{Rails.root}/config/gitlab.yml"
+  source ENV.fetch('GITLAB_CONFIG') { "#{Rails.root}/config/gitlab.yml" }
   namespace Rails.env
   class << self