qa/tasks/cephadm: use 'orch apply mon' to deploy mons

qa/tasks/cephadm: use 'orch apply mon' to deploy mons

The 'orch daemon add ...' command is not idempotent and can cause
duplicate (and failing) attempts to add the same mon.

Maintain the ability to add mons the old way for the benefit of testing
upgrades from early octopus versions of cephadm.

Signed-off-by: Sage Weil <sage@newdream.net>
(cherry picked from commit a17593a177798e5b5371c224ede40dc411626d76)