Fix socket options for websocket transport

[chmielowiec]

Fixing the following error:

  File /venv/lib/python3.8/site-packages/asyncio_mqtt/client.py", line 81, in connect
    self._client.socket().setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, 2048)
AttributeError: 'WebsocketWrapper' object has no attribute 'setsockopt'

[frederikaalund]

Hi Robert. Thanks for the pull request. 👍 Let me have a look.

Nice find. I never tested this with a WebSocket-wrapped connection.

I like the fix in general. One comment though: Let's use isinstance instead. I think that's more idiomatic. What do you think?

[chmielowiec]

Thanks for quick review! Changed according to your proposal, thanks :-) (still learning python)

Commited without tests, will test it in the evening.

[frederikaalund]

Super. 👍 Let me know how the test goes. I'll merge it afterwards.

[chmielowiec]

Tested, and of course it works perfectly, thanks for the tip!