Forward lastTransaction to app, as it is (partially) implemented there.

Update comment: it is actually used in ZODB unit tests.

git-svn-id: https://svn.erp5.org/repos/neo/trunk@1822 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/client/Storage.py

@@ -142,8 +142,8 @@ class Storage(BaseStorage.BaseStorage,
         raise NotImplementedError
 
     def lastTransaction(self):
-        # seems unused
-        raise NotImplementedError
+        # Used in ZODB unit tests
+        return self.app.lastTransaction()
 
     def _clear_temp(self):
         raise NotImplementedError