xfs: skip scrub xref if corruption already noted

Don't bother looking for cross-referencing problems if the metadata is
already corrupt or we've already found a cross-referencing problem.
Since we added a helper function for flags testing, convert existing
users to use it.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff --git a/fs/xfs/scrub/common.c b/fs/xfs/scrub/common.c
index 95625aa..2ac8576 100644
--- a/fs/xfs/scrub/common.c
+++ b/fs/xfs/scrub/common.c
@@ -737,6 +737,10 @@ xfs_scrub_should_check_xref(
 	int				*error,
 	struct xfs_btree_cur		**curpp)
 {
+	/* No point in xref if we already know we're corrupt. */
+	if (xfs_scrub_skip_xref(sc->sm))
+		return false;
+
 	if (*error == 0)
 		return true;