Show properly internationalized dates on locked discussions

Fixes CNVS-14087

Test plan:
  - Create a discussion topic
  - Set the discussion's "available from" date to a non-hour date in the
    future (e.g. 12:30pm)
  - Publish the discussion
  - View the discussion as a student and ensure that the full hour and
    minute are displayed as part of the "This topic is locked until..."
    message

Change-Id: Ic014fe90d59e111f484875291d0bb81e1d98b3c3
Reviewed-on: https://gerrit.instructure.com/40404
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Janelle Seegmiller <jseegmiller@instructure.com>
Reviewed-by: Matthew Wheeler <mwheeler@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>