If we ever rescan a stub, make sure to uncompress it

If ever the APK in /data/app is removed, we always rescan the
version on a system partition. In the case of compessed stubs,
we didn't keep track of rescanned stubs; which meant we
would never attempted to uncompress & install the full APK
after a rescan.

Add any rescanned stub to the set of known stubs so they can
correctly be uncompressed.

Bug: 186726837
Fixes: 186726837
Test: MANUAL.
Test: Boot the device
Test: Remove the uncompressed system package from /data/app
Test: Reboot the device
Test: Note that the stub is again uncompressed and replaced
Change-Id: I2b903516e2e70b659aa789120d6dd15986f9c94c