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
} == {(ti.task_id, ti.state) for ti in tis}
        for state, start_date, end_date, duration in [
            (ti.state, ti.start_date, ti.end_date, ti.duration) for ti in tis
        ]:
            if state == 'success':
                assert start_date is not None
                assert end_date is not None
                assert 0.0 == duration
            else:
                assert start_date is None
                assert end_date is None
                assert duration is None
        scheduler_job._schedule_dag_run(dr, {}, session)
        with create_session() as session:
            tis = session.query(TaskInstance).all()
        assert 5 == len(tis)
        assert {
            ('test_task_a', 'success'),
            ('test_task_b', 'success'),
            ('test_task_c', 'success'),
            ('test_task_on_execute', 'scheduled'),
            ('test_task_on_success', 'scheduled'),
        } == {(ti.task_id, ti.state) for ti in tis}
        for state, start_date, end_date, duration in [
            (ti.state, ti.start_date, ti.end_date, ti.duration) for ti in tis
        ]:
            if state == 'success':
                assert start_date is not None
                assert end_date is not None
                assert 0.0 == duration