Fall back to non-containerized cinder-backup to unblock OVB CI

Fall back to non-containerized cinder-backup to unblock OVB CI

The previous fix Ib10e4f18d967d356a15b97f58c488f8402a73356 made
multinode CI pass, but there was still an error during volume
scheduling on OVB:

OSError: [Errno 13] Permission denied: '/var/lib/cinder/conversion'

This was most likely due to cinder-volume was running on host and used
host's cinder user, while we still deployed containerized
cinder-backup and it chowned /var/lib/cinder under kolla's cinder user
whose UID doesn't match the baremetal one.

We didn't hit this issue in the multinode job because it doesn't
presently deploy cinder-backup service at all.

Co-Authored-By: Martin André <m.andre@redhat.com>
Change-Id: I9ac74d6717533f59945694b4a43fe56d7ca768c6
Closes-Bug: #1698136