ERP5Workflow: fix infinite loop because of variable renaming

the only way to escape the 'while 1' loop was depending on changes on the state
variable, which was, before this fix, using the invariant tdef instead of
transition

product/ERP5Workflow/Document/Workflow.py

@@ -323,13 +323,14 @@ class Workflow(IdAsReferenceMixin("", "prefix"), XMLObject):
   def _changeStateOf(self, document, tdef=None, kwargs=None):
     '''
     Changes state.  Can execute multiple transitions if there are
-    automatic transitions.  tdef set to None means the object
+    automatic transitions. transition set to None means the object
     was just created.
     '''
     moved_exc = None
+    transition = tdef
     while 1:
       try:
-        state = self._executeTransition(document, tdef, kwargs)
+        state = self._executeTransition(document, transition, kwargs)
       except ObjectMoved, moved_exc:
         document = moved_exc.getNewObject()
         state = self._getWorkflowStateOf(document, id_only=0)