fix module unlocking via date

test plan:
 * create a module that unlocks in the future
 * wait until the module unlocks

 * as a student (not student view)
 * from the modules page, access the module
 - the module should be unlocked and accessible by the student

fixes CNVS-13292

Change-Id: I890289f5248faab52ae5291a7a0c197c6881bc48
Reviewed-on: https://gerrit.instructure.com/35477
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>