Comment 5 for bug 1827080

Thanks Ovidiu for your precise comments, the command with delete host (compute-0) include _remove_ceph_mon() but not really remove ceph mon, need to call CephWrapper which inherit CephClient.mon_remove() which execute command: ceph mon remove {hostname}.

I have made draft gerrit: https://review.opendev.org/#/c/659094/ and soon verify the change later to fix the issue.