CentOS Stream 8 support has been dropped. Migration path will be present
in Yoga release - as a followup change.

MichaelRigart.interfaces does not support custom routes for
NetworkManager yet. It has been disabled in CI for Rocky Linux 9
temporarily.

Non-voting CentOS Stream 9 CI overcloud job is using RL9 container
images (as kolla CI is not building CS9 images anymore).

Change-Id: Idf5ee822b03ba40179803c981500a6bad37594bf