md: uuid debug statement now in processor byte order.

Previously, the uuid debug statements were printed in little-endian
format, which wasn't consistent in machines that might not be in
little-endian byte order. With this change, the output will be
consistent for all machines with different byte-ordering.

Signed-off-by: Kyungchan Koh <kkc6196@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>