Better Transition interruption

Previously, a running transition on a scene root would simply
be canceled when a new transition was started. This would result in
abrupt scene changes, especially in generic use cases where apps/widgets
would spawn multiple transitions in successive rendering frames due to
small changes in view properties.

The new approach is to check all running animations against new transitions.
If there are overlapping properties that are being set to different values,
the new animations win and the old ones are canceled. If the end values are the
same, the new animations are noop'd and the old ones are allowed to continue
as-is.

There was also improvement to capturing state while other transitions are
running, necessary in this new world where old transitions are allowed to
continue running. Now, transitions are pause()'d while values are captured,
then resume()'d after capturing is done. This allows the system to see what the
real view properties are, instead of the mid-animation values.

Change-Id: I8e77fb9c1967087a682bb26a45763005f5ca9179