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
self,
        trigger_rule,
        successes,
        skipped,
        failed,
        upstream_failed,
        done,
        flag_upstream_failed,
        expect_state,
        expect_completed,
    ):
        start_date = timezone.datetime(2016, 2, 1, 0, 0, 0)
        dag = models.DAG('test-dag', start_date=start_date)
        downstream = DummyOperator(task_id='downstream', dag=dag, owner='airflow', trigger_rule=trigger_rule)
        for i in range(5):
            task = DummyOperator(task_id=f'runme_{i}', dag=dag, owner='airflow')
            task.set_downstream(downstream)
        run_date = task.start_date + datetime.timedelta(days=5)
        ti = TI(downstream, run_date)
        dep_results = TriggerRuleDep()._evaluate_trigger_rule(  
            ti=ti,
            successes=successes,
            skipped=skipped,
            failed=failed,
            upstream_failed=upstream_failed,