This also uses the recommended machinery to set qemu instead
of relying on config file override so that we test what we
really want to test.

Change-Id: I560e4f9d0a69c347e6aaf3b970331157c1a56f18

Ussuri is Py3 everywhere. We are free to drop any py2 leftovers.

Depends-On: https://review.opendev.org/731805
Change-Id: I1a9c9a14af351cd3e8b01a40f323a82ffa673d35

AArch64 does not have a way to get cpu features from libvirt.

Change-Id: Ieed404e17e8a9829f38c03f7ee7fdb3caa3919e8

Change-Id: Ifc87adbac6bef0aaab2ad0e80739654b3e3123ad

This patches changes deploy_gate quite a bit so in reality all
deployments will now assume multinode (even if it's single node). After
that we will refactor it even further to enable easy addition of new
scenerios.

Change-Id: I1faada46e6a7aa026128b2f01d77eabb04759439