xfs: add rmap btree block detection to log recovery

Originally-From: Dave Chinner <dchinner@redhat.com>

So such blocks can be correctly identified and have their operations
structures attached to validate recovery has not resulted in a
correct block.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>