use require_dependency for reloadable constants

Change-Id: I88e032d90d7084d9a90644c555acb91bc9879d5f
Reviewed-on: https://gerrit.instructure.com/37713
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>