small adaptations to py.impl move (should eventually not be neccessary to do such things)

xdist/txnode.py

@@ -3,7 +3,7 @@
 """
 import py
 from xdist.mypickle import PickleChannel
-from py.impl.test import outcome
+from py._test import outcome
 
 class TXNode(object):
     """ Represents a Test Execution environment in the controlling process.