[DO NOT MERGE] Update Security String to 2017-04-01 on klp-dev am: 00c627eb31 am: 5be6d3bbb4 am: ed38784898  -s ours am: 84702d9919  -s ours am: d466175346 am: bc19d8140c  -s ours am: 53a64664c9
am: caff84dcbe

Change-Id: I49c8960797099da97ab452e91e7c3d4ecfde3d4f