RestrictedDashboardFragment has all the same logic coming from
RestrcitedSettingsFragment but extends from DashboardFragment.
As a result, we could use preferenceController in child class of
RestrictedDashboardFragment.
This cl also make DeviceListPreferenceFragment as child of
RestrictedDashboardFragment, which enfluences the bluetooth page.
Bug: 38041586
Test: Build
Change-Id: I01395d506176c5cc584948478f7ca16c1c7c7045
