Update Security String to 2016-05-01 in preparation for May 2016 Security OTA am: 175b780 am: 274e483 am: 08d9bea am: 6bbd684 am: f32d07d
am: 0cf7987

* commit '0cf7987b7e96d2178fbb028e36992ffb1b589b38':
  Update Security String to 2016-05-01 in preparation for May 2016 Security OTA