fix db:migrate in non-production environment

Change-Id: Ibb4465348162219b4f1da6f1a842234a7cecd78e
Reviewed-on: https://gerrit.instructure.com/37316
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>