[FIX] product_cost_usd: correctly set purchase price in multicompany

Since each company has its own purchase price, we must explicitly set the
company we are working with (the one in the sale order line) to correctly
set the purchase price.

product_cost_usd/models/sale_order_line.py

@@ -11,6 +11,7 @@ def _compute_purchase_price(self):
         """
         res = super()._compute_purchase_price()
         for line in self:
+            line = line.with_company(line.company_id)
             pricelist = line.order_id.pricelist_id
             date = line.order_id.date_order
             if not line.product_id: