mon: MonMap: mon addr and all now held by mon_info_t

mon: MonMap: mon addr and all now held by mon_info_t

Instead of keeping several maps mapping back and forth from string to
entity_addr_t for each monitor, have the monitor's address and name in
purpose-specific class, mon_info_t, and everything references it
instead.

Although the benefits may not be obvious right now, it will allow us to
add other ip addresses for the monitors a bit more easily, instead of
having to kludge around the existing structures.

We also keep compatibility with older versions by maintaining the
traditional 'mon_addr' map. This is a logical change inside the monitor,
so we can easily accomodate older monitors without having to rely on
quorum features; just needs a bit of care and foo.

Signed-off-by: Joao Eduardo Luis <joao@suse.de>