[RFE] Networking L2 Gateway does not support service node to handle unknown BUM traffic

[Maruti Kamat]

When a virtual machine on a compute node, that belongs to a network for which an l2-gateway-connection exists in the OVSDB server hardware vtep schema, pings a bare metal server on the physical network, the ARP request is broadcast to all the remote VTEPs over all the VxLAN tunnels. This unnecessarily creates a traffic to the remote VTEPs and are eventually dropped by the remote VTEPs if the bare metal is not connected to these VTEPs.
The networking l2 gateway project should introduce a service node concept that will handle such unknown BUM traffic to prevent flooding all the VxLAN tunnels.