It looks like the host_bind_override isn't being set for the flat network.
This results in the neutron linuxbridge agent to error out when trying to
attach to br-flat instead of eth2. If attaching a device to the GATEWAY_NET
network, they will be unable to communicate.
Change-Id: Ia8de61011677ec1a7d9683fdff3c3d5848e85c2e
Closes-Bug: 1754097