The play object is at self._play not self.play

Change-Id: I36bb1beda0bc99e71bd901328548e35db23fb0d5
diff --git a/zuul/ansible/callback/zuul_stream.py b/zuul/ansible/callback/zuul_stream.py
index 4744719..11da1e5 100644
--- a/zuul/ansible/callback/zuul_stream.py
+++ b/zuul/ansible/callback/zuul_stream.py
@@ -489,7 +489,7 @@
 
         # _restriction returns the parsed/compiled list of hosts after
         # applying subsets/limits
-        return self.play._variable_manager._inventory._restriction
+        return self._play._variable_manager._inventory._restriction
 
     def _dump_result_dict(self, result_dict):
         result_dict = result_dict.copy()