[FIX] stock_landed_costs: former_cost_per_unit precision

The precision of `former_cost_per_unit` should not be set. Indeed, a
stock move can contain several quants with different unit prices.
Therefore, we should not round the field when stored, otherwise the
difference per unit will not be calculated correctly.

This is a workaround since we cannot change the DB structure in stable.

opw-675222

addons/stock_landed_costs/stock_landed_costs.py

@@ -230,7 +230,8 @@ class stock_landed_cost(osv.osv):
                 if not line.move_id:
                     continue
                 per_unit = line.final_cost / line.quantity
-                diff = per_unit - line.former_cost_per_unit
+                # FORWARDPORT UP TO SAAS-10
+                diff = per_unit - (line.former_cost / line.quantity if line.quantity else 1.0)
                 quants = [quant for quant in line.move_id.quant_ids]
                 quant_dict = {}
                 for quant in quants: