VolumeDialog: Treat ring volume the same as others on icon tap

* We don't need to treat the ring volume different here,
  if it's set to 0 it already sets the ringer mode to
  vibration on supported devices.

* This makes sure that the row still displays the correct
  volume after tapping the icon, previously it only changed
  the ringer mode but left the slider at the previous value.

Change-Id: Iabd18246c41c102ad0c1f49b7525cd188b01a7c4
Signed-off-by: Jesse Chan <jc@lineageos.org>