Update MM to use IB & IPS

woohoo

Package MR: https://repo1.dso.mil/platform-one/big-bang/apps/collaboration-tools/mattermost/-/merge_requests/35

Minimal changes, just to use the IPS now and the direct IB image.

Closes https://repo1.dso.mil/platform-one/big-bang/apps/collaboration-tools/mattermost/-/issues/1