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
ti3 = dag_run.get_task_instance(task3.task_id, session)
        ti3.state = State.RUNNING
        session.flush()
        
        num_queued = job._do_scheduling(session)
        assert num_queued == 1
        
        ti2 = dag_run.get_task_instance(task2.task_id, session)
        assert ti2.state == State.QUEUED
        ti2.state = None
        session.flush()
        
        manual_run = dag.create_dagrun(
            run_type=DagRunType.MANUAL,
            execution_date=DEFAULT_DATE + timedelta(hours=1),
            state=State.RUNNING,
            session=session,
        )
        session.flush()
        num_queued = job._do_scheduling(session)
        assert num_queued == 1
        
        ti2 = dag_run.get_task_instance(task2.task_id, session)
        assert ti2.state == State.QUEUED
        
        ti1 = manual_run.get_task_instance(task1.task_id, session)
        assert ti1.state is None
@pytest.mark.xfail(reason="Work out where this goes")
def test_task_with_upstream_skip_process_task_instances():
    """