fix: Catch exception during TV shutdown

[thecode]

The following exception happens when the TV is turned off and the Quick Start+ feature is disabled:

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/aiopylgtv/webos_client.py", line 340, in ping_handler
    ping_waiter = await ws.ping()
  File "/usr/local/lib/python3.9/site-packages/websockets/legacy/protocol.py", line 657, in ping
    await self.ensure_open()
  File "/usr/local/lib/python3.9/site-packages/websockets/legacy/protocol.py", line 735, in ensure_open
    raise self.connection_closed_exc()
websockets.exceptions.ConnectionClosedOK: code = 1001 (going away), reason = server shutting down

This PR adds this exception to the silent exceptions since it is a normal behavior of the TV and should not raise an exception.

[chros73]

Thanks, I had to add to one more place, so I close this PR and add it manually.