Improve the export of stock

Today the export of the information of the stock level is done for every product which are check as "exported to magento".
The problem is when you add new product in your OpenERP catalog and you want to export it lately (maybe manually the catalog cron task is not activated). The stock level scheduler will try to export the stock of this product under magento and as the product doesn't exist in magento it will raise an error.

The solution is to export the product stock only for the product check as "exported to magento" and already synchronized