fix context_controller for rails 3

Change-Id: I0af5d47c1512f5398b634fd098b5872c639c7199
Reviewed-on: https://gerrit.instructure.com/29830
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>
QA-Review: Jacob Fugal <jacob@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>