simplify "ensure_*" method return values

[ktdreyer]

Many modules call ensure_*() helper methods, for example ensure_inheritance(). Most of these methods return a full result dict with two keys: changed (bool) and stdout_lines (list).

It's complicated and unnecessary to return a dict from all of these helper methods. This makes the code harder to understand. We can update the helper methods to return a simple list of changes instead. If a helper returns an empty list, we know there were no changes.

We only need to assemble a result dict with changed and stdout_lines keys one time: in our main method when we call module.exit_json(**result).