fix handling of serial strategy

* v2_playbook_on_play_start is called multiple times for the same UUID.
Specifically, once for each host in the play. This changes makes the
uuid unique before going to the dispatcher.

awx/lib/awx_display_callback/module.py

@@ -69,6 +69,9 @@ class BaseCallbackModule(CallbackBase):
         self.task_uuids = set()
         self.duplicate_task_counts = collections.defaultdict(lambda: 1)
 
+        self.play_uuids = set()
+        self.duplicate_play_counts = collections.defaultdict(lambda: 1)
+
     @contextlib.contextmanager
     def capture_event_data(self, event, **event_data):
         event_data.setdefault('uuid', str(uuid.uuid4()))
@@ -195,6 +198,24 @@ class BaseCallbackModule(CallbackBase):
             super(BaseCallbackModule, self).v2_playbook_on_include(included_file)
 
     def v2_playbook_on_play_start(self, play):
+        play_uuid = str(play._uuid)
+        if play_uuid in self.play_uuids:
+            # When this play UUID repeats, it means the play is using the
+            # free strategy (or serial:1) so different hosts may be running
+            # different tasks within a play (where duplicate UUIDS are common).
+            #
+            # When this is the case, modify the UUID slightly to append
+            # a counter so we can still _track_ duplicate events, but also
+            # avoid breaking the display in these scenarios.
+            self.duplicate_play_counts[play_uuid] += 1
+
+            play_uuid = '_'.join([
+                play_uuid,
+                str(self.duplicate_play_counts[play_uuid])
+            ])
+        self.play_uuids.add(play_uuid)
+        play._uuid = play_uuid
+
         self.set_play(play)
         if hasattr(play, 'hosts'):
             if isinstance(play.hosts, list):