asyncio_utils.wait_first() can mask task exception with a TimeoutError

[gsalgado]

That function will cancel all pending tasks as soon as the first task completes, but if any of the cancelled tasks doesn't terminate after the given timeout, it raises a TimeoutError, in which case we'd lose any exception raised by the first completed task. Maybe instead of raising a TimeoutError it should simply log a warning/error when cancelled tasks don't terminate after the given timeout