mds: ignore useless slave request replies during recovery

mds: ignore useless slave request replies during recovery

During mds recovers, most slave request replies are useless. If
corresponding master was not committed, slave requests will be
rollback. If corresponding master was committed, it's only
possible to receive slave request reply of type OP_COMMITTED.
The OP_COMMITTED replay is useful only if it's was triggered
by the recovering mds's resolve ack message.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>