Rescue missing database errors

While loading the Rails app we cannot assume that the gitlabhq_xxx
database exists already. If we do, `rake gitlab:setup` breaks!

This is a quick hack to make sure that fresh development setups of
GitLab (from master) will work again.

lib/gitlab/current_settings.rb

 module Gitlab
   module CurrentSettings
     def current_application_settings
+      begin
         if ActiveRecord::Base.connection.table_exists?('application_settings')
           ApplicationSetting.current ||
             ApplicationSetting.create_from_defaults
         else
           fake_application_settings
         end
+      rescue ActiveRecord::NoDatabaseError
+        fake_application_settings
+      end
     end
 
     def fake_application_settings