Fixed a test that depended on some off behavior of tpc_finish in some storages.

src/ZODB/tests/TransactionalUndoStorage.py

@@ -286,10 +286,9 @@ class TransactionalUndoStorage:
         t = Transaction()
         oids = self._begin_undos_vote(t, tid, tid1)
         self._storage.tpc_finish(t)
-        # We get the finalization stuff called an extra time:
-        eq(len(oids), 4)
-        unless(oid1 in oids)
-        unless(oid2 in oids)
+        # We may get the finalization stuff called an extra time,
+        # depending on the implementation.
+        self.assertEqual(set(oids), set((oid1, oid2)))
         data, revid1 = self._storage.load(oid1, '')
         eq(zodb_unpickle(data), MinPO(30))
         data, revid2 = self._storage.load(oid2, '')