Roles and permissions

This doesn't fix the issue for everyone, but here's a quick hack I did using a custom enrollments table that contains a user id, course id, and role. There's probably a better way to do this, but I inserted the following in /mod/quiz/overview/report.php:~354, after all the $from declarations:

INNER JOIN mdl_quiz q ON qa.quiz = q.id
INNER JOIN mdl_course c ON q.course = c.id
INNER JOIN enrollments e ON c.idnumber = e.course_id AND u.idnumber = e.user_id

This just makes sure the user actually is enrolled in the course (i.e. has a record in the enrollments table) before they display in the list.