Add support for network tunnels to OVN networks

[stgraber]

Currently we don't have support for adding VXLAN or GRE tunnels to OVN networks.

To do so we're going to need to set up the tunnel on all cluster members but only bring it up on one machine at a time to avoid loops. We can likely have the logic rely on the OVN active chassis to determine what system needs to have it on at the time.