[FIX] stock_account: default on lst_price instead of list_price

The list_price field doesn't take the extra price of variations
into account. Actually, it's not even a field of product.product.
The lst_price, however, is defined on both product.template and
product.product and does account for the extra price of variations.

OPW 659330

addons/stock_account/stock.py

@@ -129,7 +129,7 @@ class stock_move(osv.osv):
                             })[pricelist]
                 if price:
                     return price
-        return move_line.product_id.list_price
+        return move_line.product_id.lst_price
 
     def _get_invoice_line_vals(self, cr, uid, move, partner, inv_type, context=None):
         fp_obj = self.pool.get('account.fiscal.position')