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

* commit 'f32d07dd9328401525e333a34464a1d1f363e524':
  Update Security String to 2016-05-01 in preparation for May 2016 Security OTA