[DO NOT MERGE] Update security string to 2018-02-01 for mnc-dev bug:70348883...

[DO NOT MERGE] Update security string to 2018-02-01 for mnc-dev bug:70348883 am: 74f105c1 am: 6545915c am: 567d9265 am: 06602d32  -s ours am: 3980822d am: 5d59b665 am: ca5b4e79 am: dc0deb3b am: 9b1a2b4f  -s ours am: 27d97699 am: fd1ff31f
am: 5a16c534

Change-Id: I001fffdf1cd4be48d880370e52e57d51a840e277