more indexes supporting foreign keys

Change-Id: I43026dd7b489dcc87f6629f47a2a52e7b44f6c96
Reviewed-on: https://gerrit.instructure.com/39035
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Nick Cloward <ncloward@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>