Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Handle all unmatched routes with 404 method
We need this to prevent routing error when user access URL like /123 when there is no resource located under such name.
Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/23378 and https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6733.