asyncio: sync with Tulip

Backout the "Tulip issue 181: Faster create_connection()" changeset, it was a
mistake.
diff --git a/Lib/asyncio/proactor_events.py b/Lib/asyncio/proactor_events.py
index 23545c9..a80876f 100644
--- a/Lib/asyncio/proactor_events.py
+++ b/Lib/asyncio/proactor_events.py
@@ -38,7 +38,7 @@
             self._server.attach(self)
         self._loop.call_soon(self._protocol.connection_made, self)
         if waiter is not None:
-            waiter.set_result(None)
+            self._loop.call_soon(waiter._set_result_unless_cancelled, None)
 
     def _set_extra(self, sock):
         self._extra['pipe'] = sock