xfs: corruption needs to respect endianess too!

At least if we want to be able to recognize the pattern.  Add a missing
byte swap to the corruption injection case in xlog_sync.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>