In ajax queue, set the record id in ajax request's url and data at last possible moment.

Fix for issue https://github.com/spine/spine/issues/487

Because an update for a model may be put into the ajax queue before a response to a create request to the server, the id of that model might be changed after the "queueing." Instead of getting the id at the time of the "queueing" we should retrieve it at the time the ajax request actually gets called.