Fix deadlock issue in BatteryStatsHelper.

It was assumed that BatteryStatsHelper could safely call into system services.
Because it is used when dumping information from the BatteryStatsService,
this assumption was incorrect.

Now the BatteryStats object carries around the state of the energy reporting
for Bluetooth and WiFi, so BatteryStatsHelper avoids a query into WiFiManager.

b/19729960

Change-Id: I8745cf6aafeea8e862e34fe63b20056f6ba54b40