Acquire lock during service shutdown to prevent reload race condition

[NeonDaniel]

Troubleshooting logged exception:

2023-05-30 15:32:48.353 - voice - ovos_dinkum_listener.service:reload_configuration:866 - INFO - Reloading Listener
2023-05-30 15:32:48.479 - voice - ovos_dinkum_listener.service:run:263 - ERROR - voice_loop failed
Traceback (most recent call last):
  File "/home/neon/venv/lib/python3.7/site-packages/ovos_dinkum_listener/service.py", line 259, in run
    self.voice_loop.run()
  File "/home/neon/venv/lib/python3.7/site-packages/ovos_dinkum_listener/voice_loop/voice_loop.py", line 182, in run
    assert chunk is not None, "No audio from microphone"
AssertionError: No audio from microphone
2023-05-30 15:32:48.487 - voice - ovos_dinkum_listener.service:run:266 - INFO - Service stopping
2023-05-30 15:32:48.640 - voice - ovos_dinkum_listener.service:run:272 - ERROR - Service failed to start
Traceback (most recent call last):
  File "/home/neon/venv/lib/python3.7/site-packages/ovos_dinkum_listener/service.py", line 268, in run
    self._shutdown()
  File "/home/neon/venv/lib/python3.7/site-packages/ovos_dinkum_listener/service.py", line 353, in _shutdown
    self.mic.stop()
AttributeError: 'NeonSpeechClient' object has no attribute 'mic'