Interface dettach and attach events are not being triggered

[Iago Filipe]

Description
===========
Nova has two kinds of notification publishing mechanisms to RabbitMQ, legacy and non-legacy (unversioned and versioned). The network interface attach/detach events are triggered only in the versioned RabbitMQ topic.

Seen on Ussuri and above (till master)

The problem seems to be on nova.compute.manager.ComputeManager._detach_interface and nova.compute.manager.ComputeManager._attach_interface, is not calling self._notify_about_instance_usage which is used to push messages to the unversioned topic.

Besides that, on nova.rpc.LegacyValidatingNotifier the allowed_legacy_notification_event_types doesn't contains the interface events (described in the documentation[1]).

Therefore, the solution is: add the event to the array described above and call the notify_about_instance_usage inside attach and detach methods on ComputeManager.

Expected result
===============
Interface events published to unversioned and versioned topics.

Actual result
=============
Interface events published only to the versioned topic.

[1]https://docs.openstack.org/nova/latest/reference/notifications.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/nova/+/823200

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Iago Filipe <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/nova/+/823200