Use separate icon group for signal/battery in QS header

This reverts the terrible hack that reattaches the system icons when
expanding QS. This primarily fixes that the alpha of the icons was
wrong when closing the shade, but also fixes flickering when expanding
the shade.

Bug: 17338013
Change-Id: Ifcbe03eca43ed7639059734e23d740c1b8a7a9de
5 files changed