When a failed request (EBADR or ENOTBLK) is unlocked/canceled instead of
retried, there may be other lkb's waiting on the rsb_lookup list for it
to complete.  A call to confirm_master() is needed to move on to the next
waiting lkb since the current one won't be retried.
Signed-off-by: David Teigland <teigland@redhat.com>