Kolla provides a flag, enable_neutron_provider_networks, to enable
virtualised compute nodes to access provider (e.g. flat, VLAN) networks.
In kayobe, we now connect compute nodes to the external networks when
this flag is set. This ensures that the OVS network on compute nodes
is wired into the external networks.
Change-Id: Ida3d8eb2e2bfc95f6007c105ce410b3e5d360afe
Story: 2002636
Task: 22278
2803950422