Simplify anacondatest root_console to always use tty3
    
    Rawhide KDE lives now have the desktop on tty2, and the installer
    environment tty3 now has a shell (in Ye Olde Times it didn't, not
    sure when that changed but it's the case at least back to F31).
    So let's make our lives simple and just always use tty3 here.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>