Override the state description of volume seekbar.

This overrides the state description of seekbar in order to adjust the
progress percentage. The percentage of seekbar is not matching with the
percentage said by talkback feature when the volume changes. This CL
rounds the percentage to match what is said by talkback.

Bug: 285458191
Test: Enabled talkback and checked percentages of sliders of all sounds
and vibrations volumes. Video attached in bug link.
Test: atest VolumeSeekBarPreferenceTest.

Change-Id: Iedcf3eccb13b7f8ee1a4ca521f0783c55d7a1902