Method to close unclosed tests

This is based on http://tracker.moodle.org/browse/MDL-24587
Once unclosed tests have been identified, the normal procedure is for the admin to log in as that specific user, click on the unclosed test and close it. This ensures that the score comes in.

It would be handy to have a method to close several unclosed tests from the grading area of that test without having to go through the current long procedure