xfs: fix force shutdown handling in xfs_end_io

Ensure ioend->io_error gets propagated back to e.g. AIO completions.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_aops.c

@@ -189,7 +189,7 @@ xfs_end_io(
 	int		error = 0;
 
 	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
-		error = -EIO;
+		ioend->io_error = -EIO;
 		goto done;
 	}
 	if (ioend->io_error)