Recovers on boot when scan of data app fails

Prior to this change, system apps that had updated versions installed
that could not be scanned on boot, did not have a fallback mechanism to
restore the system app. With this change, we prepare for such a scenario
and restore the system app using the existing "expecting better"
mechanism.

Test: manual; muck with an APK in /data/app and reboot.
Bug: 117471712
Change-Id: Ic50880cc04e92003c2a20869cf38835af7ce3ccb