ipa-server-install: deprecate manual setting of master KDC password
    
    Option '-P' was used in older version of FreeIPA to set up KDC master password
    during server install. This is no longer neccessary or desirable since the
    password of sufficient strength can be generated automatically during
    installation.
    
    https://fedorahosted.org/freeipa/ticket/4516
    
    Reviewed-By: Petr Vobornik <pvoborni@redhat.com>