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
done, fail = False, False
        run_ti_and_assert(date1, date1, date1, 0, State.UP_FOR_RESCHEDULE, 0, 1)
        done, fail = False, False
        run_ti_and_assert(date2, date1, date2, 60, State.UP_FOR_RESCHEDULE, 0, 2)
        done, fail = False, False
        run_ti_and_assert(date3, date1, date3, 120, State.UP_FOR_RESCHEDULE, 0, 3)
        done, fail = True, False
        run_ti_and_assert(date4, date1, date4, 180, State.SUCCESS, 1, 0)
        
        dag.clear()
        ti.refresh_from_db()
        assert ti.state == State.NONE
        assert ti._try_number == 1
        
        
        
        done, fail = False, False
        run_ti_and_assert(date1, date1, date1, 0, State.UP_FOR_RESCHEDULE, 1, 1)
        done, fail = False, True
        run_ti_and_assert(date2, date1, date2, 60, State.UP_FOR_RETRY, 2, 0)
        done, fail = False, False
        run_ti_and_assert(date3, date3, date3, 0, State.UP_FOR_RESCHEDULE, 2, 1)
        done, fail = True, False
        run_ti_and_assert(date4, date3, date4, 60, State.SUCCESS, 3, 0)
    def test_reschedule_handling_clear_reschedules(self):