CI: workaround for upgrade test backward compatibility

The new CI does not define k8s_cluster group, so it relies on
kubernetes-sigs/kubespray#11559.

This does not work for upgrade testing (which use the previous release).
We can revert this commit after 2.27.0

tests/cloud_playbooks/roles/packet-ci/tasks/create-vms.yml

 ---
 - name: Start vms for CI job
   vars:
+    # Workaround for compatibility when testing upgrades with old == before e9d406ed088d4291ef1d9018c170a4deed2bf928
+    # TODO: drop after 2.27.0
+    legacy_groups: "{{ (['kube_control_plane', 'kube_node', 'calico_rr'] | intersect(item) | length > 0) | ternary(['k8s_cluster'], []) }}"
     tvars:
-      kubespray_groups: "{{ item }}"
+      kubespray_groups: "{{ item + legacy_groups }}"
   kubernetes.core.k8s:
     definition: "{{ lookup('template', 'vm.yml.j2', template_vars=tvars) }}"
   loop: "{{ scenarios[mode | d('default')] }}"