zero: updated KeyDisabler
zero: updated KeyDisabler

 * Corrected package-name of FileUtils
 * Check if the file is writeable before writing

TeamNexus/android_device_samsung_zero-common,TeamNexus/android_device_samsung_zero-common,TeamNexus/android_device_samsung_zero-common,TeamNexus/android_device_samsung_zero-common,TeamNexus/android_device_samsung_zero-common