Point API entry to neutron-lib API Reference
Point API entry to neutron-lib API Reference

This change replaces the networking-bgpvpn API reference in the
devref with a link to the API reference published from neutron-lib.

Change-Id: I3efda347df007609f5e11a07813068a12cba736a

openstack/networking-bgpvpn,openstack/networking-bgpvpn,openstack/networking-bgpvpn