Adjust total consumed power to avoid double-counting

The definition of SystemBatteryConsumer.getConsumedPower()
has been changed to include power attributed to apps.
That power is also included in UidBatteryConsumers, so we
ended up double-counting power attributed to apps.

Bug: 183235836
Test: atest FrameworksCoreTests:com.android.internal.os.BatteryStatsTests
Change-Id: Ib99b3ce910b62528241e271bdb3b925a9ac01830