Bug 1088623 - Adding lockscreen libary to 2.1 a=testonly

It seems that there was a bug in marionnette (which seems to be fixed) when enabling the lockscreen from settings.
https://github.com/mozilla-b2g/gaia/pull/25493/files#diff-cdfedcf8e16c089b48922a5c4895e2ccR94

lockscreen.enable: false + lockscreen.relock() seems to be the same than lockscreen.enable: true. The problem is that lockscreen.relock is not working in 2.1.