* Updating tower_job_template.py
* tower_job_template: Update parameter version_added to 2.7
* Ensure that unset credentials aren't passed
Passing empty strings for unset credentials causes ValueErrors as
the API expects an integer. Don't pass unset credentials
* add additional test coverage for tower modules
* add test coverage for the tower_credential module
* add test coverage for the tower_user module
* fix a bug in py3 for tower_credential when ssh_key_data is specified
* add test coverage for tower_host, tower_label, and tower_project
* add test coverage for tower_inventory and tower_job_template
* add more test coverage for tower modules
- tower_job_launch
- tower_job_list
- tower_job_wait
- tower_job_cancel
* add a check mode/version assertion for tower module integration tests
* add test coverage for the tower_role module
* add test coverage for the tower_group module
* add more integration test edge cases for various tower modules
* give the job_wait module more time before failing
* randomize passwords in the tower_user and tower_group tests
