[FIX] sale_stock: duplicate qty

- Create a stockable product, create a SO selling 1 unit.
- Confirm the SO, validate the Picking 1 => delivered qty is 1
- Return Picking 1 and validate Picking 2 => delivered qty is 1
- Return Picking 2 and validate Picking 3 => delivered qty is 2

The delivered quantity should remain 1.

opw-715685

addons/sale_stock/sale_stock.py

@@ -197,7 +197,8 @@ class SaleOrderLine(models.Model):
             #Note that we don't decrease quantity for customer returns on purpose: these are exeptions that must be treated manually. Indeed,
             #modifying automatically the delivered quantity may trigger an automatic reinvoicing (refund) of the SO, which is definitively not wanted
             if move.location_dest_id.usage == "customer":
-                qty += self.env['product.uom']._compute_qty_obj(move.product_uom, move.product_uom_qty, self.product_uom)
+                if not move.origin_returned_move_id:
+                    qty += self.env['product.uom']._compute_qty_obj(move.product_uom, move.product_uom_qty, self.product_uom)
         return qty
 
     @api.multi