Settings: fixed battery stats app list

The check of mAppListGroup getPreferenceCount is no longer working
after we added other options on this page. Add a separate counter to get
back the full possible list of 12 apps

Change-Id: I679b01deec0f52d4fa2012a31b7b305f8fe176b5

Conflicts:
	src/com/android/settings/fuelgauge/PowerUsageSummary.java