That syncs the Neutron code with the latest neutron-lib version
released (3.8.0).
This patch also adds the "network.ha" definition extension to
the tests core plugin.
NOTE: both LP bugs must be fixed in one patch to fix the unit
tests CI job.
Closes-Bug: #2033493
Closes-Bug: #2033508
Change-Id: Ie22d9bcb943205e20380b92dc33d48f398a86470