fix an indefinite hang which would wait for events although no events

are pending - this happened if items arrive very quickly while
the "reschedule-event" tried unconditionally avoiding a busy-loop
and not schedule new work.

xdist/__init__.py

@@ -1,3 +1,3 @@
 #
-__version__ = "1.0"
+__version__ = "1.1"
 

xdist/dsession.py

@@ -55,7 +55,9 @@ class LoopState(object):
 
     def pytest_rescheduleitems(self, items):
         self.colitems[:] = items + self.colitems
-        self.dowork = False # avoid busywait
+        for pending in self.dsession.node2pending.values():
+            if pending:
+                self.dowork = False # avoid busywait, nodes still have work
 
 class ExitFirstInterrupt(KeyboardInterrupt):
     pass