Default groups.oo_etcd_to_config when setting embedded_etcd in control plane upgrade.

playbooks/common/openshift-cluster/upgrades/upgrade_control_plane.yml

@@ -24,7 +24,7 @@
   - openshift_facts:
       role: master
       local_facts:
-        embedded_etcd: "{{ groups.oo_etcd_to_config | length == 0 }}"
+        embedded_etcd: "{{ groups.oo_etcd_to_config | default([]) | length == 0 }}"
 
 - name: Backup etcd
   hosts: etcd_hosts_to_backup