Remove the need for docker

This change moves our one tox-molecule job to simply depending on
the zuul tox job. To ensure we're not depending on the docker
driver at all, docker has been replaced with podman in the
tripleo_redhat_enforce test job.

Change-Id: I590a500b397d22d2e6fd4336f306caadcb690f45
Signed-off-by: Kevin Carter <kecarter@redhat.com>

tripleo_ansible/roles/tripleo_redhat_enforce/molecule/default/molecule.yml

@@ -1,6 +1,6 @@
 ---
 driver:
-  name: docker
+  name: podman
 
 log: true
 

zuul.d/molecule.yaml

@@ -538,7 +538,7 @@
     - ^zuul.d/molecule.yaml
     name: tripleo-ansible-centos-8-role-addition
     nodeset: centos-8
-    parent: tox-molecule
+    parent: tox
     timeout: 1800
     vars:
       tox_envlist: role-addition