ensure course's account and root account are in associated_courses

fixes CNVS-3273

test plan:
 * create a course in a sub account
 * delete all course_account_associations for that course
 * clear your cache, and restart your server
 * as an admin in only that account, you should be able to
   edit the course (even though you won't see it in the course
   list for the account)

Change-Id: I26120fedbd9556c18e08cecf5ff4f14a960d334c
Reviewed-on: https://gerrit.instructure.com/34486
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>