[FIX] mrp_multi_level: adapt tests to recent upstream changes.

After odoo/odoo@1ed6dbe
we need to explicitly set routes in the propoer order becouse while
in the cache there are not yet sorted by sequence (it requires flush
to the database, which we cannot do in a test).

mrp_multi_level/tests/test_mrp_multi_level.py

@@ -444,8 +444,10 @@ def test_17_supply_method(self):
         self.fp_4.route_ids = [(4, self.env.ref("mrp.route_warehouse0_manufacture").id)]
         product_mrp_area._compute_supply_method()
         self.assertEqual(product_mrp_area.supply_method, "manufacture")
+        # because of the issue discussed here https://github.com/odoo/odoo/pull/188846
+        # we need to apply routes explicitly in the proper order (by sequence)
         self.fp_4.route_ids = [
-            (4, self.env.ref("purchase_stock.route_warehouse0_buy").id)
+            (6, 0, (self.env.ref("stock.route_warehouse0_mto") + self.env.ref("purchase_stock.route_warehouse0_buy") + self.env.ref("mrp.route_warehouse0_manufacture")).ids)
         ]
         product_mrp_area._compute_supply_method()
         self.assertEqual(product_mrp_area.supply_method, "buy")