Use default package in BatteryEntry

Before this cl, we use the first package name if there is a name
list in BatterySipper.

We should use BatteryEntry.defaultPackageName instead, which could
describle the batterysipper more accurately.

Bug: 62417935
Test: RunSettingsRoboTests
Change-Id: I44fa151c0cf8f14cba305f179c7e94e5bc3ce434