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
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)
        
        current_children = set(current_process.children(recursive=True)) - set(old_children)
        assert not current_children
    @mock.patch('airflow.jobs.scheduler_job.TaskCallbackRequest')
    @mock.patch('airflow.jobs.scheduler_job.Stats.incr')
    def test_process_executor_events(self, mock_stats_incr, mock_task_callback):
        dag_id = "test_process_executor_events"
        dag_id2 = "test_process_executor_events_2"
        task_id_1 = 'dummy_task'
        dag = DAG(dag_id=dag_id, start_date=DEFAULT_DATE, full_filepath="/test_path1/")
        dag2 = DAG(dag_id=dag_id2, start_date=DEFAULT_DATE, full_filepath="/test_path1/")
        task1 = DummyOperator(dag=dag, task_id=task_id_1)
        DummyOperator(dag=dag2, task_id=task_id_1)
        dag.fileloc = "/test_path1/"
        dag2.fileloc = "/test_path1/"
        executor = MockExecutor(do_update=False)
        task_callback = mock.MagicMock()
        mock_task_callback.return_value = task_callback
        scheduler = SchedulerJob(executor=executor)
        scheduler.processor_agent = mock.MagicMock()
        session = settings.Session()
        dag.sync_to_db(session=session)