Initialize the volume seekbar preference max and progress.

When the media stream is set, initialize the preference max and progress
with the streams current value. Otherwise, when we initialize the seekbar
volumizer, it will first set the seekbar max to 0 and progress to 0,
then update with the correct value, which will result in the jank that
is seen when the sound settings are displayed.

Change-Id: I515c97bbc6ec38bbe92755e3d7cb53bb13ac52d0
Fix: 34035654
Test: make RunSettingsRoboTests