Fix the battery icon on the battery page when low battery

Check power-saving state for drawing the battery icon on the battery page.
It will draw red + icon as status-bar did when battery saver is on.

Change-Id: Iee4a17c8e5cb3c8ee5d978eb23e3980597d09a1c
Fixes: 77150820
Test: Manual test, atest BatteryMeterViewTest BatteryHeaderPreferenceControllerTest