Fix animation and layoutTransition issues.

There were some subtle timing issues in animators with ending animations that
were not completely initialized (possibly because a startDelay'd animator
was ended before the delay elapsed).
Also, LayoutTransition had bugs around running a transition on a container
while a previously-started transition was still in progress. This could result
in some minor artifacts or crash bugs, depending on the durations and delays set
on the transition animations.

Change-Id: Ic6a69601f1ce9a55db15fff6b8ed25950b354491