xfs/841: actually compare the new filesystem contents to the proto dir

We should confirm that the directory tree was correctly copied into the
new filesystem, not just that the image files all have the same
checksum.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zorro Lang <zlang@kernel.org>