camera: Keep touch focus intact during back-to-back ZSL shots

 * If ZSL is enabled, we should not resetTouchFocus between shots.
 * Instead, re-kick the timer for each shot. If I set a focus point,
   I want that point to stick while I take a succession of shots.

Change-Id: I407bb1e248cc902355d0294f47b071cc8a32fac3