Update tests for optimum efficiency.

.travis.yml

@@ -7,9 +7,9 @@ env:
     - ROLE_NAME: certbot
   matrix:
     - MOLECULE_DISTRO: centos7
-      MOLECULE_DOCKER_COMMAND: /usr/lib/systemd/systemd
     - MOLECULE_DISTRO: centos6
       MOLECULE_PLAYBOOK: playbook-source-install.yml
+    - MOLECULE_DISTRO: ubuntu1804
     - MOLECULE_DISTRO: ubuntu1604
     - MOLECULE_DISTRO: ubuntu1404
       MOLECULE_PLAYBOOK: playbook-source-install.yml

molecule/default/molecule.yml

@@ -9,8 +9,10 @@ lint:
     config-file: molecule/default/yaml-lint.yml
 platforms:
   - name: instance
-    image: geerlingguy/docker-${MOLECULE_DISTRO:-centos7}-ansible
-    command: ${MOLECULE_DOCKER_COMMAND:-"sleep infinity"}
+    image: "geerlingguy/docker-${MOLECULE_DISTRO:-centos7}-ansible:latest"
+    command: ${MOLECULE_DOCKER_COMMAND:-""}
+    volumes:
+      - /sys/fs/cgroup:/sys/fs/cgroup:ro
     privileged: true
     pre_build_image: true
 provisioner: