Performance improvement using in-operator on dicts

Just a small cleanup for the existing occurrences.

Using the in-operator for hash lookups is faster than using .keys()
http://stackoverflow.com/questions/29314269/why-do-key-in-dict-and-key-in-dict-keys-have-the-same-output

lib/ansible/utils/module_docs.py

@@ -104,7 +104,7 @@ def get_docstring(filename, verbose=False):
                                         doc['notes'] = []
                                     doc['notes'].extend(notes)
 
-                            if 'options' not in fragment.keys():
+                            if 'options' not in fragment:
                                 raise Exception("missing options in fragment, possibly misformatted?")
 
                             for key, value in fragment.items():