Product renewal link omit product node IDs in renewal reminder e-mails.

ec_recurring_token_values() returns an incorrect value for the product renewal URL as it assumes the existence of an variable '$product', which, as far as I can see, is not defined anywhere. The attached patch uses the defined variable $entry to get the node id, producing a correct URL (although the renewal page itself is still broken for me, but that's probably a job for a different bug)