Fix 6580421: make sure MultiWaveView.reset() makes handle visible

This fixes a bug where sometimes the handle wasn't visble in the
incoming call screen.  The problem was that the animation was
interrupted on its transition from alpha = 0 to alpha = 1 by reset()
and the new handle animation wasn't started.

Change-Id: I3ab4259db1115da20e7f54b91bbfe3b496940214