fix user merge spec for rails 3

Change-Id: I5e2b595521d785bb050828d838c85a6a189235f5
Reviewed-on: https://gerrit.instructure.com/30821
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>