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
dag = DAG(
            'test_task_start_end_stats',
            start_date=DEFAULT_DATE,
            end_date=DEFAULT_DATE + datetime.timedelta(days=10),
        )
        op = DummyOperator(task_id='dummy_op', dag=dag)
        dag.create_dagrun(
            run_id='manual__' + DEFAULT_DATE.isoformat(),
            execution_date=DEFAULT_DATE,
            start_date=DEFAULT_DATE,
            state=State.RUNNING,
            external_trigger=False,
        )
        ti = TI(task=op, execution_date=DEFAULT_DATE)
        ti.state = State.RUNNING
        session = settings.Session()
        session.merge(ti)
        session.commit()
        ti._run_raw_task()
        ti.refresh_from_db()
        stats_mock.assert_called_with(f'ti.finish.{dag.dag_id}.{op.task_id}.{ti.state}')
        assert call(f'ti.start.{dag.dag_id}.{op.task_id}') in stats_mock.mock_calls
        assert stats_mock.call_count == 5
    def test_generate_command_default_param(self):