Fix assumption in test_commands about primary keys

        self.assertTrue(data["message"].endswith("with task_id 1."))
        self.assertEqual(data["task_id"], 1)

If any other test creates (and then deletes) WorkRequest objects, the primary key of the task created in the test_command_output_successful_case unit test will not be 1. Although the objects have been deleted, the database keeps information about the highest seen pk value and adds a new database object at pk+1, not at 1. See https://stackoverflow.com/questions/27735375/django-model-instances-primary-keys-do-not-reset-to-1-after-all-instances-are-de

Fix the check to retrieve the actual pk of the created item.