Don't output complex items in the summary line

When iterating over complex objects, printing them out in the task
summary line is very noisy and hard to follow.

Change-Id: I4ae748f167ee03ba97a4bcbf2417dae0271e24a5

playbooks/zuul-stream/fixtures/test-stream.yaml

@@ -20,6 +20,13 @@
         - item2
         - item3
 
+    - name: Loop with complex items
+      command: "echo {{ item.name }}"
+      with_items:
+        - name: complex1
+        - name: complex2
+        - name: complex3
+
     - name: Run a shell task with an ansible python exception
       command: echo foo
       args:

zuul/ansible/callback/zuul_stream.py

@@ -428,10 +428,16 @@ class CallbackModule(default.CallbackModule):
                                    indent=2, sort_keys=True),
                     status=status)
         else:
-            self._log_message(
-                result,
-                "Item: {item} Runtime: {delta}"
-                " Start: {start} End: {end}".format(**result_dict))
+            if isinstance(result_dict['item'], str):
+                self._log_message(
+                    result,
+                    "Item: {item} Runtime: {delta}"
+                    " Start: {start} End: {end}".format(**result_dict))
+            else:
+                self._log_message(
+                    result,
+                    "Item: Runtime: {delta} Start: {start} End: {end}".format(
+                        **result_dict))
 
         if self._deferred_result:
             self._process_deferred(result)