This drops support for the os-virtual-interfaces compute REST API
which has been deprecated since Newton:
I1a8a44530be29292561e90d6f7bd7ed512a88ee3
Now it returns 410 response.
Unit tests are removed and the functional API sample test is just
asserting the 410 response now. The API sample docs are left intact
since the API reference still builds from those and can be considered
more or less branchless, so people looking at the API reference can
apply it to older deployments of nova before os-virtual-interfaces was
removed.
Depends-On: https://review.openstack.org/571556/
Part of blueprint remove-nova-network
Change-Id: Id7f94a643e5d7b8a842c0f4a5c9f796d6566b365
4c93003ede