Comment 3 for bug 1202648

In cinder/volume/api.py, we have this code in create():
        if availability_zone is None:
            availability_zone = CONF.storage_availability_zone
        else:
            self._check_availabilty_zone(availability_zone)

I think Michael's suggestion is that if availability_zone is None and we are creating from snapshot, we should use the snapshot's availability zone, not what's in CONF. I would extend this to clone operations as well.