Set container_cli for undercloud

This patch allows to set container_cli in undercloud.conf, during the
upgrade process. So later we can start testing the upgrade of an
undercloud from rocky/docker to stein/podman.

Change-Id: Idbcd1f16b35013b929d7eb8e9cbac9daf675b08e

tasks/upgrade/configure_uc_containers.yml

@@ -10,6 +10,14 @@
   failed_when: false
   register: defined_insecure_registry
 
+- name: set container_cli for undercloud
+  ini_file:
+    path: "{{ undercloud_conf }}"
+    section: DEFAULT
+    option: container_cli
+    value: "{{ undercloud_container_cli }}"
+  when: undercloud_container_cli is defined
+
 - block:
     - name: set containers file for undercloud
       ini_file: