Swap seekbar vert padding to keep height fixed

Reduce the vertical padding of the seekbar when it's enabled by 2dp to
account for the extra height in the track. That way the height of the
SeekBar view is always 33dp.

This has a nice side effect of properly setting the height of the track
when resuming.

Bug: 160242262
Test: manual
Change-Id: I9b6888f2a6bf5fb118075dea3f849618350ec18b