tests: tests switch_to_containers against octopus
tests: tests switch_to_containers against octopus

since we have container images for ceph@master, we shouldn't use
nautilus anymore.

Signed-off-by: Guillaume Abrioux <30a9df5a0293a6108675377fa1673f7aa713f915@redhat.com>

ceph/ceph-ansible,ceph/ceph-ansible