WIXBUG:4412 - Improve progress.

The goal here was to make sure that each container/payload only contributes to the overall progress once.  It's possible that a container/payload never contributes.  For example, if a container never has to be acquired because all of its payloads are already cached or a non-vital package is skipped.

WixStdBA had to be updated since it didn't set its cache progress variable to 100% on OnCacheComplete.