Fix Event loop closed bug

Once again, I run into this really hard to debug issue w/ asyncio. The
previous bug in shell was in fact a issue w/ ayncio.sleep() that prevent
task to close.. (don't ask my why... in previous version this sleep was
needed to close tasks...

libs/lib/xaal/lib/aioengine.py

@@ -270,7 +270,6 @@ class AsyncEngine(core.EngineMixin):
         for task in self.all_tasks():
             if task != self._watchdog_task:
                 task.cancel()
-                await asyncio.sleep(0.1)
 
     def sigkill_handler(self, signal, frame):
         print("", end="\r")  # remove the uggly ^C