This tests fails occasionally on mysql at least:

https://github.com/apache/airflow/pull/11555/checks?check_run_id=1260840314#step:9:1125

```
=================================== FAILURES ===================================
_____________ TestSchedulerJob.test_no_orphan_process_will_be_left _____________

self = <tests.jobs.test_scheduler_job.TestSchedulerJob testMethod=test_no_orphan_process_will_be_left>

    def test_no_orphan_process_will_be_left(self):
        empty_dir = mkdtemp()
        current_process = psutil.Process()
        old_children = current_process.children(recursive=True)
        scheduler = SchedulerJob(subdir=empty_dir,
                                 num_runs=1,
                                 executor=MockExecutor(do_update=False))
        scheduler.run()
        shutil.rmtree(empty_dir)
    
        # Remove potential noise created by previous tests.
        current_children = set(current_process.children(recursive=True)) - set(
            old_children)
>       self.assertFalse(current_children)
E       AssertionError: {psutil.Process(pid=3474, name='/usr/local/bin/', status='running', started='19:26:22')} is not false

tests/jobs/test_scheduler_job.py:871: AssertionError
```



tests/jobs/test_scheduler_job.py
with mock.patch.object(settings, "STORE_DAG_CODE", False):
            scheduler.dagbag.bag_dag(dag, root_dag=dag)
            scheduler.dagbag.sync_to_db()
        session = settings.Session()
        orm_dag = session.query(DagModel).get(dag.dag_id)
        assert orm_dag is not None
        
        scheduler._create_dag_runs([orm_dag], session)
        drs = DagRun.find(dag_id=dag.dag_id, session=session)
        assert len(drs) == 1
        dr = drs[0]
        ti = dr.get_task_instance('dummy')
        ti.set_state(state, session)
        scheduler._schedule_dag_run(dr, {}, session)
        expected_callback = DagCallbackRequest(
            full_filepath=dr.dag.fileloc,
            dag_id=dr.dag_id,
            is_failure_callback=bool(state == State.FAILED),
            execution_date=dr.execution_date,
            msg=expected_callback_msg,
        )
        
        scheduler.processor_agent.send_callback_to_execute.assert_called_once_with(expected_callback)
        
        
        scheduler._send_sla_callbacks_to_processor.assert_called_once_with(dag)
        session.rollback()
        session.close()
    @parameterized.expand([(State.SUCCESS,), (State.FAILED,)])
    def test_dagrun_callbacks_are_not_added_when_callbacks_are_not_defined(self, state):