fix scope(:find, :select/:group/:shard/:conditions) for rails 3

Change-Id: I746004e5d6ab6ac0a4d7d557a799f878c0a84501
Reviewed-on: https://gerrit.instructure.com/29401
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>