fix references to the default shard settings for rails 3

Change-Id: Ie35fd3d9255c934d29799f99596fb65e75181947
Reviewed-on: https://gerrit.instructure.com/29599
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>