Ensure second route group OID is correct (sonic-net#3380)

What I did
When grabbing the second route group OID, ensure that it is distinct from the first route group OID

Why I did it
The order in which DB keys are returned is not deterministic, so blindly taking the last key returned will sometimes lead to selecting the wrong OID

tests/dash/test_dash_route_group.py

@@ -44,7 +44,11 @@ def test_rebind_eni_route_group(dash_db: DashDB):
 
     dash_db.set_app_db_entry(APP_DASH_ROUTE_GROUP_TABLE_NAME, ROUTE_GROUP2, ROUTE_GROUP2_CONFIG)
     dash_db.set_app_db_entry(APP_DASH_ROUTE_TABLE_NAME, ROUTE_GROUP2, OUTBOUND_ROUTE_PREFIX1, ROUTE_VNET_CONFIG_UNDERLAY_SIP)
-    rg2_oid = dash_db.wait_for_asic_db_keys("ASIC_STATE:SAI_OBJECT_TYPE_OUTBOUND_ROUTING_GROUP", min_keys=2)[1]
+    oids = dash_db.wait_for_asic_db_keys("ASIC_STATE:SAI_OBJECT_TYPE_OUTBOUND_ROUTING_GROUP", min_keys=2)
+    for oid in oids:
+        if oid != rg1_oid:
+            rg2_oid = oid
+            break
 
     dash_db.set_app_db_entry(APP_DASH_ENI_ROUTE_TABLE_NAME, ENI_ID, ENI_ROUTE_GROUP1_CONFIG)