Add new policy: Update Time Restrictions

Allows administrators to set time intervals in which the managed
devices should not check for updates. Unless the updates are forced.

BUG=chromium:852860
TEST=Tested locally and used unit tests
CQ-DEPEND=CL:1097698

Change-Id: Ibd9ff26fb537a966f86d9a824845fa4cf7f92d8e
Reviewed-on: https://chromium-review.googlesource.com/1097990
Commit-Queue: Adolfo Higueros <adokar@google.com>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568308}
9 files changed