demo: add testing of UDP

demo/m6/re6stnet.conf

 log m6/
 run m6/run
 state m6/
-pp 1194 tcp
 ca ca.crt
 cert m6/cert.crt
 key m6/cert.key
 default
+disable-proto none
+client 10.0.0.2,1194,udp
 # TODO: Run a DHCPv4 client on machine9. Unfortunately, isc-dhcp-client 4.2.4
 #       fails with "Bind socket to interface: No such device"
 daemon "exec dnsmasq -d8 - -i $re6stnet_iface -F 192.168.42.2,192.168.42.254,255.255.255.0,infinite -F ${re6stnet_subnet%/*},ra-only,${re6stnet_subnet#*/},1d -O option:router,192.168.42.1 -l m6/dnsmasq.leases"

demo/registry/re6stnet.conf

@@ -6,3 +6,4 @@ ca ca.crt
 cert registry/cert.crt
 key registry/cert.key
 gateway
+disable-proto none