Move task_launch_lock into initial TaskRecord (#2930)

There's no reason for it to be omitted and added later, and this style is
more defensive.

parsl/dataflow/dflow.py

@@ -984,6 +984,7 @@ def submit(self,
                        'joins': None,
                        'try_id': 0,
                        'id': task_id,
+                       'task_launch_lock': threading.Lock(),
                        'time_invoked': datetime.datetime.now(),
                        'time_returned': None,
                        'try_time_launched': None,
@@ -1029,8 +1030,6 @@ def submit(self,
                                                               task_record['func_name'],
                                                               waiting_message))
 
-        task_record['task_launch_lock'] = threading.Lock()
-
         app_fu.add_done_callback(partial(self.handle_app_update, task_record))
         self.update_task_state(task_record, States.pending)
         logger.debug("Task {} set to pending state with AppFuture: {}".format(task_id, task_record['app_fu']))