run_sync does not clean up the pending task after run_until_complete is interrupted

[shingo78]

When the wrapped method (like BlockingKernelClient.get_shell_msg) is interrupted by KeyboardInterrupt(Ctrl+C), the event loop is interrupted, and the task ( asyncio.Task ) becomes a pending state.
If I call the wrapped method again, it does not return.

I think run_sync should cancel the pending task.
https://stackoverflow.com/questions/30765606/whats-the-correct-way-to-clean-up-after-an-interrupted-event-loop

[davidbrochart]

Thanks for reporting the issue @shingo78. Do you want to try and open a PR? That would be great.

[shingo78]

Thanks. Please review it.