fix collaborations_controller_spec for rails 3

Change-Id: Ib6523c256cd9be2532ad969c9c8fa3dd5ed5962f
Reviewed-on: https://gerrit.instructure.com/29826
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>