feat(config): implement diff mode support

plugins/modules/config.py

@@ -222,6 +222,8 @@ def run_module():
                 old_value = None
             else:
                 old_value = rc.stdout
+            if old_value is None and new_value is None:
+                continue
             if old_value == v:
                 continue
             result['changed'] = True