fix lib/limporter specs for rails 3

Change-Id: Ie68af02a84ce4149869f4ade51d51c44c3f9b022
Reviewed-on: https://gerrit.instructure.com/29649
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>