spec: fixes to course_spec for rails 3

Change-Id: I441ada2d03f7eb5243a3657168368e640a457f5f
Reviewed-on: https://gerrit.instructure.com/29404
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>