simple-slave: Change g-i-s' home directory ownership to created user
    
    We do this at the end of the gnome-initial-setup special session,
    before logging in to the newly created user account.
    
    This allows the user session's gnome-initial-setup instance to
    manipulate files here.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=701473