b834bd5048
The external network extension's API definition was rehomed into neutron-lib with I9933b91d1e82db3891b3b72f06e94316e56a4f15. This patch consumes it, switch over to neutron-lib's modules and removing the rehomed code in neutron. NeutronLibImpact Change-Id: I696b52265b9528082cd2524f05febe2338376488