[FIX] product: default quantity on pricelist item

- Create a new pricelist for a new currency
- Set the 'Sale Price' option to 'A single sale price per product', so
  that the user cannot see the pricelist details
- Sell 0.5 unit of the product with the new pricelist

The pricelist is not correctly applied.

This is because the default minimum quantity is 1. Once the user is
selling less than 1 unit, the pricelist is not applied.

opw-1825353

addons/product/pricelist.py

@@ -340,7 +340,7 @@ class product_pricelist_item(osv.osv):
 
     _defaults = {
         'base': 'list_price',
-        'min_quantity': 1,
+        'min_quantity': 0,
         'sequence': 5,
         'price_discount': 0,
         'applied_on': '3_global',