Optional tower cli (#3)

* Allow running tests without tower_cli

* patch up test mutability

* Fix test import error, warning mock

* flake8 error

Update documentation for non-converted modules

awx_collection/plugins/modules/tower_workflow_launch.py

@@ -44,6 +44,8 @@ options:
 
 requirements:
   - "python >= 2.6"
+  - ansible-tower-cli >= 3.0.2
+
 extends_documentation_fragment: awx.awx.auth
 '''