osd: do full check in do_op

osd: do full check in do_op

1. The current pool_last_map_marked_full tracking is buggy.
2. We need to recheck this each time we consider the op, not just when it
is received off the wire.  Otherwise, we might get a message, queue it
for some reason, get a map indicating the cluster or pool is full, and
then requeue and process the op instead of discarding it.
3. For now, silently drop ops when failsafe check fails. This will lead to
stalled client IO.  This needs a more robust fix.

Signed-off-by: Sage Weil <sage@redhat.com>