[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
am: 5d59b6650b

Change-Id: I4ff20889f9e42cc1520844aacc11cab3bdcf0fd0