Add Disks and NICs to _AllUUIDObjects

Since disks and NICs have UUIDs, they must be considered
to _AllUUIDObjects.

Signed-off-by: Christos Stavrakakis <cstavr@grnet.gr>
Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Reviewed-by: Helga Velroyen <helgav@google.com>