more fk indexes

also fix an old migration that should have ran on all shards

Change-Id: Ib4305c4f1b84ba0cfd525d0f552cfc21d365dc24
Reviewed-on: https://gerrit.instructure.com/37492
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Reviewed-by: Brian Palmer <brianp@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>