Ensure root folders get added in split archives

Make sure that we add the root folder itself to get the perms and
SELinux contexts before splitting to a second archive.

Change-Id: Id93a9f9b4767b61bba38eb0cf7306c81a8540a3c
fix getting and setting contexts in selinux

recreate lost+found with selinux contexts

Change-Id: I19e8696d47319dfb641520956c8a27c2a796a0c3