[Robustness] protect get battery stats from DeadSystemException

In some corner cases, we will receive the DeadSystemException from
BatteryStatService when invoking getBatteryUsageStats() method. Before
this issue is resolved by BatteryStatService team, we will add some
protections to avoid Settings app is crashed.

Bug: 195306545
Bug: 195467687
Test: make SettingsRoboTests
Change-Id: I75fcf63f4f69d86d6dce0e12bd4d738b1219ae47