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 am: 87582a8
am: 880e914

* commit '880e914ec6b8ce053ad5b766a2907afaf0c79673':
  Update Security String to 2016-04-02 in preparation for April 2016 Security OTA v2 - kernel updates with patches for CVE-2015-1805