verify settings: fix etcd assertion when implicity etcd group

When the etcd group is not specified we assume it's kube_control_plane.
In that case, etcd still can't be even, so instead of only checking the
etcd group we need to default to kube_control_plane

roles/kubernetes/preinstall/tasks/0040-verify-settings.yml

@@ -74,10 +74,10 @@
 
 - name: Stop if even number of etcd hosts
   assert:
-    that: groups.etcd | length is not divisibleby 2
+    that: groups.get('etcd', groups.kube_control_plane) | length is not divisibleby 2
+  run_once: true
   when:
     - not ignore_assert_errors
-    - inventory_hostname in groups.get('etcd',[])
 
 - name: Stop if memory is too small for control plane nodes
   assert: