xfs: clean up broken eearly-exit code in the inode btree scrubber

Corrupt inode chunks should cause us to exit early after setting the
CORRUPT flag on the scrub state.  While we're at it, collapse trivial
helpers.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>