overcloud/deploy: use overcloud_container_cli to find out which env to load

Some TripleO CI jobs (OVB + HA with Pacemaker) will still need Docker on
the Overcloud until we get CentOS 8.
So this patch will load docker.yaml or podman.yaml depending on what is
overcloud_container_cli.

Depends-On: I80b07c83aae752b2b327a4570bc3df230f6a6319
Change-Id: I15c4c1b7f4c24865759c7225f7212241c9ff63c6

roles/overcloud-deploy/tasks/pre-deploy.yml

@@ -195,8 +195,8 @@
       {% else %}
       -e {{ working_dir }}/containers-prepare-parameter.yaml
       {% endif %}
-      {% if release not in ['pike', 'queens', 'rocky'] and overcloud_container_cli == 'podman' %}
-      -e {{ overcloud_templates_path }}/environments/podman.yaml
+      {% if release not in ['pike', 'queens', 'rocky'] %}
+      -e {{ overcloud_templates_path }}/environments/{{ overcloud_container_cli | default('docker') }}.yaml
       {% endif %}
   when:
     - containerized_overcloud|bool