Fix test_order_by_success_case to accomodate scylla

Scylla does not support statement with opposite ordering direction for
the same collumn:
SELECT * FROM table ORDER BY a ASC, a DESC;

tests/integration/cqlengine/query/test_queryset.py

@@ -608,7 +608,7 @@ def test_order_by_success_case(self):
         for model, expect in zip(q, expected_order):
             assert model.attempt_id == expect
 
-        q = q.order_by('-attempt_id')
+        q = q.order_by().order_by('-attempt_id')
         expected_order.reverse()
         for model, expect in zip(q, expected_order):
             assert model.attempt_id == expect