Fix test for innodb

uid is guaranteed to be unique, not to be consecutive.
For some reason  innodb will give a uid of 3 for that test.
The real test is thus to test it is different, but not to test the equality

master/buildbot/test/unit/test_db_users.py

@@ -208,7 +208,7 @@ def test_addUser_existing_identifier(self):
 
         def check_user(uid):
             # creates a new user
-            self.assertEqual(uid, 2)
+            self.assertNotEqual(uid, 1)
 
             def thd(conn):
                 users_tbl = self.db.model.users