Record Bluetooth Cumulative Stats Properly

updateBluetoothStateLocked does not check for null values, causing
NPE. This patch reverts part of the change in 3445570. Instead, an
update method is added to LongSamplingCounter, which accepts
cumulative values.
Fixes: 75963520
Test: LongSamplingCounterTest

Change-Id: I89eba8e20f8f055c60f4ff250653345a22536189
4 files changed