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/models/test_taskinstance.py
raise
            ti.refresh_from_db()
            assert ti.state == expected_state
            assert ti._try_number == expected_try_number
            assert ti.try_number == expected_try_number + 1
            assert ti.start_date == expected_start_date
            assert ti.end_date == expected_end_date
            assert ti.duration == expected_duration
            trs = TaskReschedule.find_for_task_instance(ti)  
            assert len(trs) == expected_task_reschedule_count
        date1 = timezone.utcnow()
        done, fail = False, False
        run_ti_and_assert(date1, date1, date1, 0, State.UP_FOR_RESCHEDULE, 0, 1)
        
        dag.clear()
        ti.refresh_from_db()
        assert ti.state == State.NONE
        assert ti._try_number == 0
        
        trs = TaskReschedule.find_for_task_instance(ti)  
        assert not trs
    def test_depends_on_past(self):
        dag = DAG(dag_id='test_depends_on_past', start_date=DEFAULT_DATE)
        task = DummyOperator(
            task_id='test_dop_task',
            dag=dag,
            depends_on_past=True,
        )
        dag.clear()
        run_date = task.start_date + datetime.timedelta(days=5)