Handle KeyboardInterrupts in the cli better (#1391)

Addresses an issue with how `asyncclick` deals with `KeyboardInterrupt`
errors. Instead of the `click.main` receiving `KeyboardInterrupt` it
receives `CancelledError` because it's a task running inside the loop.

Also ensures that discovery catches the `CancelledError` and closes the
http clients.

kasa/discover.py

@@ -498,7 +498,7 @@ class Discover:
         try:
             _LOGGER.debug("Waiting %s seconds for responses...", discovery_timeout)
             await protocol.wait_for_discovery_to_complete()
-        except KasaException as ex:
+        except (KasaException, asyncio.CancelledError) as ex:
             for device in protocol.discovered_devices.values():
                 await device.protocol.close()
             raise ex