[EE] Change gitlab_sign_in to sign_in
EE counterpart of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12369
Edited by Robert Speicher
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
EE counterpart of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12369