fixup volume stream linking

- Make the SeekBarVolumizer move notification and ringer streams when
 linked and moving ringer.

- Fix initial state causing volume stream seek bar to be set to 0
  initially

- Clean up AudioService initialization code

Change-Id: Ia11a7a392e5eb3ef862147843e365d5f20eaf90a
Signed-off-by: Roman Birg <roman@cyngn.com>
(cherry picked from commit be753d6b)