monitor should send monmap updates when the monmap is updated
1. create a cluster with 3 mon, 1 osd
2. create another mon manually, wait until the quorum is formed. update the ceph.conf also, otherwise the "ceph" cli won't be able to get updated monmap
3. "ceph mon remove a"
4. osd.0 won't be able to connect to cluster anymore.
if the updated monmap is sent to osd.0, osd.0 will be able to switch to the new monitor, even it is not in its initial monmap.