kea-dhcp4 should not grant leases for packets that have neither hardware addr not client id

This issue emanates from #805. The packet in question is a DHCPREQUEST that has hardware type of 0, are 0 length hardware address and no client id. Link to the packet below:

https://gitlab.isc.org/isc-projects/kea/uploads/5ce316e25212db266b3329e7384e84bd/packet10.pkt

It has no ciaddr, no giaddr (though hops=2), and no address option, yet kea-dhcp4 grants it a lease. kea-dhcp4 currently requires either hardware address or a client-id. Handing out a lease when neither is present isn't viable. It should sanity check for these two and drop packets without them.