Update Mattermost for 8.17 and 8.16 omnibus
This is a security update for Mattermost 3.6.x used by GitLab 8.17 and 8.16.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
This is a security update for Mattermost 3.6.x used by GitLab 8.17 and 8.16.