rails3 spec fixes for submission comments controller

Change-Id: Ibb6b4371bcf2716a4056bb4604809a1369441e42
Reviewed-on: https://gerrit.instructure.com/29769
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>
QA-Review: Derek DeVries <ddevries@instructure.com>