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
assert ti._try_number == 1
        assert ti.try_number == 2
        
        run_with_error(ti)
        assert ti.state == State.FAILED
        assert ti._try_number == 2
        assert ti.try_number == 3
        
        
        dag.clear()
        
        run_with_error(ti)
        assert ti.state == State.UP_FOR_RETRY
        assert ti._try_number == 3
        assert ti.try_number == 4
        
        run_with_error(ti)
        ti.refresh_from_db()
        assert ti.state == State.FAILED
        assert ti._try_number == 4
        assert ti.try_number == 5
        assert RenderedTaskInstanceFields.get_templated_fields(ti) == expected_rendered_ti_fields
    def test_next_retry_datetime(self):
        delay = datetime.timedelta(seconds=30)
        max_delay = datetime.timedelta(minutes=60)
        dag = models.DAG(dag_id='fail_dag')
        task = BashOperator(
            task_id='task_with_exp_backoff_and_max_delay',
            bash_command='exit 1',
            retries=3,