[FIX] sale_order_price_recalculation: Use write instead of update

This way, all tracking events can take place.

Closes #848

sale_order_price_recalculation/models/sale_order.py

@@ -20,7 +20,7 @@ def recalculate_prices(self):
             # we make this to isolate changed values:
             line2.product_uom_change()
             line2._onchange_discount()
-            line.update({
+            line.write({
                 'price_unit': line2.price_unit,
                 'discount': line2.discount,
             })