[DO NOT MERGE] Update security string to 2018-02-01 for mnc-dev bug:70348883 am: 74f105c16f am: 6545915c0b am: 567d926508 am: 06602d3239  -s ours
am: 3980822dff

Change-Id: I80365112878b90cdd62979372cfe275d3e22eaa8