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
"""
        DagRuns with one successful and one future root task -> SUCCESS
        Noted: the DagRun state could be still in running state during CI.
        """
        clear_db_dags()
        dag_id = 'test_dagrun_states_root_future'
        dag = self.dagbag.get_dag(dag_id)
        dag.sync_to_db()
        scheduler = SchedulerJob(num_runs=1, executor=self.null_exec, subdir=dag.fileloc)
        scheduler.run()
        first_run = DagRun.find(dag_id=dag_id, execution_date=DEFAULT_DATE)[0]
        ti_ids = [(ti.task_id, ti.state) for ti in first_run.get_task_instances()]
        assert ti_ids == [('current', State.SUCCESS)]
        assert first_run.state in [State.SUCCESS, State.RUNNING]
    def test_dagrun_deadlock_ignore_depends_on_past_advance_ex_date(self):