fix calendars_controller_spec for rails 3

Change-Id: If8a0540ff2cb6e5a9b45c36146f6a4fb83a94046
Reviewed-on: https://gerrit.instructure.com/29824
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>