[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 am: 2f222829e0 am: 69586d29d7  -s ours
am: 8f510b8ca1

Change-Id: I76e4a8e5ef538561bdf93a0b62d5ebb9171288b3