asyncio: Recover eventloop's ability to work with callbacks.

Actually, coroutine support for call_soon() is a hack, in big asyncio coroutine
should be wrapped in Task object.

asyncio/asyncio.py

@@ -46,6 +46,9 @@ class EventLoop:
             delay = t - tnow
             if delay > 0:
                 self.wait(delay)
+            if callable(cb):
+                cb(*args)
+            else:
                 delay = 0
                 try:
                     ret = next(cb)