Wait an extra 2 minutes for the installer 'beta nag' screen
    
    There seems to be an issue in Rawhide ATM which can cause the
    'beta nag' screen to take a very long time to appear. Bump the
    timeout to avoid tests failing on this.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1666112
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>