Make sure to only return attributevalues that are on the actual produ…

…ct to avoid transferring

attributesvalues from parent to child.

oscarapi/serializers/product.py

@@ -317,7 +317,7 @@ def update(self, instance, validated_data):
         # child product.
         product.attr._dirty.clear()  # pylint: disable=protected-access
         product.attr.save()
-        return list(product.attr.get_values().filter(attribute__code__in=attr_codes))
+        return list(product.attribute_values.filter(attribute__code__in=attr_codes))
 
 
 class ProductAttributeValueSerializer(OscarModelSerializer):