Pass the file-diffing flag as an arg to checkit.

testsuite/devices.test

@@ -28,9 +28,7 @@ mknod "$fromdir/block2" b 42 73 || test_skipped "Can't create block device node
 mknod "$fromdir/block3" b 105 73 || test_skipped "Can't create block device node unless root"
 mkfifo "$fromdir/fifo" || test_skipped "Can't run mkfifo"
 
-touch "$tmpdir/do_not_diff_the_files"
-
-checkit "$RSYNC -aHvv \"$fromdir/\" \"$todir/\"" "$fromdir" "$todir"
+checkit "$RSYNC -aHvv \"$fromdir/\" \"$todir/\"" "$fromdir" "$todir" skip_file_diff
 
 # The script would have aborted on error, so getting here means we've won.
 exit 0