adtrust: remove nttrustpartner parameter
    
    MS-ADTS spec requires that TrustPartner field should be equal to the
    commonName (cn) of the trust. We used it a bit wrongly to express
    trust relationship between parent and child domains. In fact, we
    have parent-child relationship recorded in the DN (child domains
    are part of the parent domain's container).
    
    Remove the argument that was never used externally but only supplied by
    trust-specific code inside the IPA framework.
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>