don't use update_without_callbacks cause it's gone in rails 3

Change-Id: I0af3c874c33c993da827ad72ab74731520a87782
Reviewed-on: https://gerrit.instructure.com/30337
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Josh Simpson <jsimpson@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>