Fix minor transition bugs

TransitionGroup.setDuration() was not propagating the new duration to
future child transitions correctly.

Also, Fade should restore a fully-opaque value when a transition ends, to prevent
the problem of mid-stream canceled transitions causing vie3ws to get stuck with partially
faded-in alpha values.

Issue #9755995 Transitions: TransitionGroup.setDuration() not handled correctly
Issue #9756655 Transitions: handle fading cancelation better

Change-Id: Id44569c6f4152a26ee382d04c30a2f035a1ebcf3