don't extend current_version_unidirectional

Change-Id: I410c7784cb988e077a470eead493d15c5682e427
Reviewed-on: https://gerrit.instructure.com/28860
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>