change the way SCORM saving error works

Instead of asking the student to resubmit, just keep resubmitting every time the student acknowledges the warning.
The warning ('scorm.failed save') tells the student that pressing OK will attempt to save again, and reassures them that their previous answers are still saved.

There's a "Saving..." overlay while the request is going, but since Moodle uses synchronous calls, the browser never gets a chance to show it :(
give the "saving..." message half a chance to be shown