Better warning when deleting a user
Warn the administrator better when deleting a user. Fixes: https://github.com/gitlabhq/gitlabhq/issues/4295
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Warn the administrator better when deleting a user. Fixes: https://github.com/gitlabhq/gitlabhq/issues/4295