Get rid of separate max mon limit; use the system limit instead. This
allows mounts when there are lots of mon addrs provided by mount.ceph (as
with a host with lots of A/AAAA records).
Signed-off-by: Sage Weil <sage@newdream.net>
Writeback doesn't work without the bdi set, and writeback on
umount doesn't work if we unregister the bdi too early.
Signed-off-by: Sage Weil <sage@newdream.net>