cephadm-adopt: make the playbook idempotent

cephadm-adopt: make the playbook idempotent

If the cephadm-adopt.yml fails during the first execution and some
daemons have already been adopted by cephadm then we can't rerun
the playbook because the old container won't exist anymore.

Error: no container with name or ID ceph-mon-xxx found: no such container

If the daemons are adopted then the old systemd unit doesn't exist anymore
so any call to that unit with systemd will fail.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1918424
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>
(cherry picked from commit 6886700a002e5d59bed5c18d082f8902bd57978c)