ci-multinode: Use qemu virtualisation

Most multinode environments will use nested virtualisation, and we
can't guarantee that nested KVM support is available. Use QEMU as a
lowest common denominator.

We might consider setting this dynamically based on the hypervisor in
future.

Author: markgoddard

etc/kayobe/environments/ci-multinode/kolla/globals.yml

@@ -1,4 +1,9 @@
 ---
+# Most development environments will use nested virtualisation, and we can't
+# guarantee that nested KVM support is available. Use QEMU as a lowest common
+# denominator.
+nova_compute_virt_type: qemu
+
 # Reduce the control plane's memory footprint by limiting the number of worker
 # processes to two per-service when running in a VM.
 openstack_service_workers: "{% raw %}{{ [ansible_facts.processor_vcpus, 2 if ansible_facts.virtualization_role == 'guest' else 5] | min }}{% endraw %}"