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
other_dag = self.dagbag.get_dag('test_task_start_date_scheduling')
            other_dag.is_paused_upon_creation = True
            other_dag.sync_to_db()
            scheduler = SchedulerJob(executor=self.null_exec, subdir=dag.fileloc, num_runs=1)
            scheduler.run()
            
            assert len(session.query(TaskInstance).filter(TaskInstance.dag_id == dag_id).all()) == 0
            session.commit()
            assert [] == self.null_exec.sorted_tasks
            
            
            
            
            bf_exec = MockExecutor()
            backfill = BackfillJob(executor=bf_exec, dag=dag, start_date=DEFAULT_DATE, end_date=DEFAULT_DATE)
            backfill.run()
            
            assert len(session.query(TaskInstance).filter(TaskInstance.dag_id == dag_id).all()) == 1
            assert [
                (TaskInstanceKey(dag.dag_id, 'dummy', DEFAULT_DATE, 1), (State.SUCCESS, None)),
            ] == bf_exec.sorted_tasks
            session.commit()
            scheduler = SchedulerJob(dag.fileloc, executor=self.null_exec, num_runs=1)
            scheduler.run()
            
            assert len(session.query(TaskInstance).filter(TaskInstance.dag_id == dag_id).all()) == 1
            session.commit()
            assert [] == self.null_exec.sorted_tasks
    @pytest.mark.quarantined
    def test_scheduler_task_start_date(self):