Follow UpdatePolicy messages into the ASG they impact to give users fast feedback on failed instance rollouts.

[askreet]

We just had someone internally hit an issue where CF timed out doing an UpdatePolicy rolling instance updates out. It would be neat if the code that follows the StackEvents for failures could notice when an UPDATE_IN_PROGRESS is referring to a rolling update and then follow events on that Auto-Scaling Group. It looks like the message format is: ^Rolling update initiated. -- too bad amazon doesn't return something less likely to change.