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

* commit '6bbd684464a1307f074e6c173a9147d6e2a626f1':
  Update Security String to 2016-05-01 in preparation for May 2016 Security OTA