xfs: mark a data structure sick if there are cross-referencing errors

If scrub observes cross-referencing errors while scanning a data
structure, mark the data structure sick.  There's /something/
inconsistent, even if we can't really tell what it is.

Fixes: 4860a05d ("xfs: scrub/repair should update filesystem metadata health")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>