MDL-9375 (and dups) - Each attempt builds on last with multi-page quizzes gives the wrong score on the second attempt. It turns out that this was already fixed in Moodle 1.9 (part of commit 1.115 -> 1.116) so I have just backported the relevant changes. I have tested that this fixes the reported problem. I have not had time to test that it does not break one of the other billion possible combinations of settings possible with the quiz. Code review and testing welcome.