Update Security String to 2016-04-02 in preparation for April 2016 Security OTA v2 - kernel updates with patches for CVE-2015-1805 am: 2b71be5 am: df28b90 am: b90d094 am: fa24625
am: d7bf980

* commit 'd7bf9800f4f5fdc83b2ffb163207025459b26b36':
  Update Security String to 2016-04-02 in preparation for April 2016 Security OTA v2 - kernel updates with patches for CVE-2015-1805