Remember having done full-data as well as key/value app backups

The "what have we ever succesfully backed up?" log is used to determine
whether we can do an install-time restore from the currently-live dataset
rather than go back to the ancestral dataset (if any).  We now track
apps that have gotten a successful full-data backup through the transport,
not just key/value backups.

Bug 17263823

Change-Id: If21350a8dd8aaa4ed02fb74101617e935920e4ae