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
{'A': State.SUCCESS, 'B': State.NONE, 'C': State.NONE, 'D': State.NONE},
                None,
                "D -> C -> B & A -> B, when A runs but C isn't QUEUED yet, B shouldn't be QUEUED.",
            ),
            (
                {('scheduler', 'schedule_after_task_execution'): 'True'},
                {'A': 'C', 'B': 'C'},
                {'A': State.QUEUED, 'B': State.FAILED, 'C': State.NONE},
                {'A': State.SUCCESS, 'B': State.FAILED, 'C': State.UPSTREAM_FAILED},
                None,
                "A -> C & B -> C, when A is QUEUED but B has FAILED, C is marked UPSTREAM_FAILED.",
            ),
        ]
    )
    def test_fast_follow(
        self, conf, dependencies, init_state, first_run_state, second_run_state, error_message
    ):
        with conf_vars(conf):
            session = settings.Session()
            dag = DAG('test_dagrun_fast_follow', start_date=DEFAULT_DATE)
            dag_model = DagModel(
                dag_id=dag.dag_id,
                next_dagrun=dag.start_date,
                is_active=True,
            )
            session.add(dag_model)
            session.flush()
            python_callable = lambda: True
            with dag:
                task_a = PythonOperator(task_id='A', python_callable=python_callable)