Zero duration animations snap to end value when started

A recent change to seeking behavior altered the logic of
setCurrentPlayTime() (which is called when animations are first
started) to set the current animated fraction to 0 for 0-duration
animations. This fix ensures that 0-duration animations snap to
their end value (fraction == 1) instead, matching the behavior
prior to the seeking fix.

Issue #18542543 Animations with 0 duration stay in initial state when calling setCurrentPlayTime(0)

Change-Id: I9916d962cf46453a9e3e1207f58baf16f4a5830a