Rename Dockerfile.j2 to Dockerfile

Unify check_undercloud_conf deprecated_params testing with all others

Change-Id: I11d7dc75bb0a49961bc72909c5af2db1db378b18

roles/check_undercloud_conf/molecule/deprecated_params/molecule.yml

@@ -10,6 +10,7 @@ platforms:
     image: ubi8/ubi-init
     registry:
       url: registry.access.redhat.com
+    dockerfile: Dockerfile
     pkg_extras: python*-setuptools python*-pyyaml
     volumes:
       - /etc/ci/mirror_info.sh:/etc/ci/mirror_info.sh:ro