add ubuntu 18.04 support

After adding ubuntu 18.04 to all roles that were dependencies of mss-server-low, I believe should expect further role development to support ubuntu 18.04 out of the box.

{{cookiecutter.role_name}}/molecule/default/molecule.yml

@@ -17,6 +17,9 @@ platforms:
   - name: ${USER}-${UUID}-{{cookiecutter.role_name | replace('.','') | replace('_','')}}-centos6
     box: centos/6
 
+  - name: ${USER}-${UUID}-{{cookiecutter.role_name | replace('.','') | replace('_','')}}-ubuntu1804
+    box: ubuntu/bionic64
+
   - name: ${USER}-${UUID}-{{cookiecutter.role_name | replace('.','') | replace('_','')}}-ubuntu1604
     box: ubuntu/xenial64