virtualize.sh: find GW in router NIC list
virtualize.sh: find GW in router NIC list

Use the router network list to identify the correct gateway for a given
network.
Previously we were using the IP of the very first network, but this was not
accurate enough.

redhat-cip/infra-virt,redhat-cip/infra-virt,enovance/infra-virt,enovance/infra-virt