Use `:empty_project` where possible in feature specs
Like https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10836, but for the spec/feature
sub-folders.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Like https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10836, but for the spec/feature
sub-folders.