Don't check for 389-instances.
    
    We no longer need to enforce that no 389-ds instances exist on an IPA
    server. Checking that the ports exist should be enough.
    
    This used to be one mechanism we used to check to see if IPA was already
    installed. We have a better mechanism now.
    
    https://fedorahosted.org/freeipa/ticket/1735