spec: fix folder_spec for rails 3

Change-Id: I330f2629ab55ffece4df56ef5c07fc177dd34413
Reviewed-on: https://gerrit.instructure.com/29433
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>