Update colorPrimary in watch

1. Update colorPrimary in watch. This value is only used for icons and
switch background on watch.

2. Replace hard coded color and disable alpha in switch track.

3. Rename watch_switch_track_mtrl_alpha to be  watch_switch_track_mtrl
since it's no longer a alpha mask.

Change-Id: Ia1eaae62a934c89e3ca6cc8736b256c552f0329b