xfs: xfs_scrub_iallocbt_xref_rmap_inodes should use xref_set_corrupt

In xfs_scrub_iallocbt_xref_rmap_inodes we're checking inodes against
rmap records, so we should use xfs_scrub_btree_xref_set_corrupt if we
encounter discrepancies here so that we know that it's a cross
referencing error, not necessarily a corruption in the inobt itself.

The userspace xfs_scrub program will try to repair outright corruptions
in the agi/inobt prior to phase 3 so that the inode scan will proceed.
If only a cross-referencing error is noted, the repair program defers
the repair attempt until it can check the other space metadata at least
once.

It is therefore essential that the inobt scrubber can correctly
distinguish between corruptions and "unable to cross-reference something
else with this inobt".  The same reasoning applies to "xfs: record inode
buf errors as a xref error in inobt scrubber".

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>