DeskClock: Fix Clock style Analog doesn't work in Daydream settings.

After start screen saver and enter Dream setting again, the default
preference xml file was moved (moveSharedPreferencesFrom()), the
preference fragment will create a new default xml file, the default
Style is still digital,while actual has be change to Analog.

setStorageDeviceProtected for PreferenceFragment.

Change-Id: Ib008b8e92f894146572fb666aab361d10c27ef92
CRs-Fixed: 1045044