reset self.tpc_phase in _finish() to resolve known errors in both issues repoze#31 and repoze#30

Author: vietdt

repoze/sendmail/delivery.py

@@ -102,6 +102,7 @@ def _finish(self, final_state):
         if self.transaction is None:
             raise ValueError("Not in a transaction")
         self.state = final_state
+        self.tpc_phase = 0
 
     def commit(self, trans):
         if self.transaction is None: