Delay migration until after user is prepared.

We don't have a vold connection early in the PackageManagerService
constructor, so we can only migrate the system user at boot.  We now
migrate other users only after they're explicitly unlocked by
UserManagerService.

Bug: 27330415
Change-Id: I29f21714acf65a598b8df496af0f7d2cb1d247c4
1 file changed