Futures scheduled after shutdown.

[Lorak-mmk]

Sometimes after executing integration tests, there is an error printed to the terminal:

============================================================================ 528 passed, 98 skipped, 101 warnings in 132.65s (0:02:12) =============================================================================
Exception in thread Task Scheduler:
Traceback (most recent call last):
  File "/usr/lib64/python3.11/threading.py", line 1038, in _bootstrap_inner
    self.run()
  File "/home/karolbaryla/repos/python-driver/venv/lib64/python3.11/site-packages/cassandra/cluster.py", line 4302, in run
    future = self._executor.submit(fn, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/concurrent/futures/thread.py", line 167, in submit
    raise RuntimeError('cannot schedule new futures after shutdown')
RuntimeError: cannot schedule new futures after shutdown