Improve volume slider

In the Settings, the Preference#onBindViewHolder will be invoked
3 times when a preference is getting highlighted. This caused that a
disabled volume slider becomes enabled after getting highlighted.

This change is to optimize the init method of VolumeSeekbarPreference
to speed up the initial process and fix the unexpected behavior.

Bug: 275352565
Test: manual test and robotest pass
Change-Id: I77f28386f6d6e4a45297f1ca7bcbaf16ed6136a4