Prevent cancellation of task with timeout in asyncio runner. (#35045)

I am yet unclear why on new python/os/websocket we do not get
a timeout error, however from what I could tell, wait_for would
cancel the websocket.recv and that stops instead of throwing
a timeout exception, resulting in a full success result.

Making this change seems to make the test TestPurposefulFailureExtraReportingOnToggle
pass on my machine (well ... fail as expected instead of passing with a
successful stop)

Co-authored-by: Andrei Litvin <[email protected]>