Fix for WooCommerce2 + where get_product cant return an instance of WC_Product and the property to hold the ID is in lowercase.  This causes the property to not correct set. 

When the property isn't correct set it breaks the magic method __get ( which in turn stops the correct return values of calls to SKU or any other meta. This includes updating stock ).
Merge pull request #3269 from zogot/fix/IDPropertyWooCommerce2

Fix for WooCommerce 2+ for the ID property