Hide power menu from secure lockscreen (2/2)

- Made disabled by default

Special thanks to @UtkarshGupta in this commit: https://github.com/omnirom/android_packages_apps_Settings/commit/4ff8b5b485c28903a3560c4f93f0b12ed8f70cce

Change-Id: I5d19cc0ccdc3b89599cb6dd4a73b2b477ae72324