[DO NOT MERGE] Update Security String to 2017-04-01 for mnc-dev am: 06a57496e6 am: a3e5f184eb am: 775af5ae5b am: 6ebebd3ee3  -s ours
am: 8dd075b1c0

Change-Id: Id946441c5f667c756397327f03223b4f5d0660a3