Show battery percentage in QS header

This change temporarily short-circuits the logic to show battery
percentage instead of estimate in the QS header. This is in
order to avoid exposing visibly broken behavior to users while a
more comprehensive solution for the underlying issue is worked on.

Bug: 282044659
Test: manual
Change-Id: I2fde71ea940be38fbf85028c1f9cc1b993712c02