[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 am: 89005ae01c am: dc8df2ef3d
am: 5699a49c08

Change-Id: Ife69cfa81c778b75ee5980810a262f7443f44af2