server-install: remove broken no-pkinit check
    
    Don't check for no-pkinit option in case pkinit cert file was
    provided. Setting no-pkinit is prohibited in this case, so without
    this fix we have an impossible option-check if we want to provide
    an own pkinit certificate and private key.
    
    https://pagure.io/freeipa/issue/6807
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>