Create foreman_user module (#296)

* Create foreman_user module

Create a new module for managing users. In order to change password we
need to force the `password` field to be sent during POST but that
field is not included when doing GET, so we put it in `check_missing`.

plugins/module_utils/foreman_helper.py

@@ -192,7 +192,7 @@ def update_resource(self, resource, old_entity, entity_dict, check_missing, chec
         if check_missing is not None:
             for key in check_missing:
                 if key in entity_dict and key not in volatile_entity.keys():
-                    volatile_entity[key] = new_value
+                    volatile_entity[key] = entity_dict[key]
                     fields.append(key)
         if len(fields) > 0:
             new_data = {'id': entity_id}