spec: fix sis_imports_api_spec for rails 3

Change-Id: Ie9dbc99745b35c278154b4171507fa0688d34e54
Reviewed-on: https://gerrit.instructure.com/30909
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>