rbd: send ceph monitor addresses with connection info

Previously we relied on a ceph configuration file on the compute host
for this information. Sending the info directly from cinder makes more
complex setups with multiple ceph clusters talking to the same compute
hosts possible.

Refresh the monitor addresses for each initialize_connection() call,
since monitors may be added or removed while cinder-volume is
running.

Fixes: bug 1077817
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>

Change-Id: I34a1fa16ce1f4524ba25832faf3129303e755100
Merge "rbd: send ceph monitor addresses with connection info"