shrink-mon: support updating ceph config file after mon removal

shrink-mon: support updating ceph config file after mon removal

This add the possibility for users to opt in/out about monitor removal
from the ceph config file on all nodes.

By default, it won't update the ceph config file. If you want the playbook
to update it, you have to pass the extra variable `-e shrink_mon_update_cfg=true`

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