CellularBatteryStats: Address API council feedback

Bug: 144925883
Test: Build pass, device boots up
atest TelephonyMetricsTest

Change-Id: Iac5904a3397a42aa5f015cb53bb63318f5c377a4
Merged-In: Iac5904a3397a42aa5f015cb53bb63318f5c377a4
(cherry picked from commit 84dc30fedeb284f63651171476909361a6ac8c03)
4 files changed