Stable seek bar positioning

Touching the thumb on the Seek bar prevents the thumb from immediately jumping to a new position and changing the progress of the Seek bar.

Test: Place your finger on the seek bar thumb so that your finger touches the thumb. Take your finger away. Seek bar should not change progress and thumb's position.
Place your finger on the seek bar thumb so that your finger touches the thumb. Seek bar should not change progress and thumb's position. Then, without lifting your finger from the screen, move your finger towards the maximum or minimum value. Seek bar thumb should follow your finger while maintaining its position relative to your finger.

Change-Id: Ia72d247662ad5b8dd66d0b0578098b9a2b6060cd