Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Required for https://gitlab.com/gitlab-org/gitaly/issues/238, https://gitlab.com/gitlab-org/gitaly/issues/141 and https://gitlab.com/gitlab-org/gitaly/issues/252
Closes https://gitlab.com/gitlab-org/omnibus-gitlab/issues/2444
/cc @andrewn