Also revert back to _domain_obj in testing

Author: bouwew

tests/test_smile.py

@@ -277,7 +277,7 @@ async def connect(
 
         if not timeout:
             assert smile._timeout == 30  # pylint: disable=protected-access
-        assert smile.domain_objects is None  # pylint: disable=protected-access
+        assert smile._domain_objects is None  # pylint: disable=protected-access
         assert smile.smile_type is None
 
         # Connect to the smile