Git commits in Moodle 3.8.6 by Dan Marsden

commit c67361661277c42cf169d0cb007f86d222a4f01d
Author: Dan Marsden <dan@danmarsden.com>
Date:   Fri, 03 Jul 2020 07:23:17 +0800
Tag:    v3.8.6

MDL-69641 grade: fix slow query.