vault-add: set the default vault type on the client side if none was given
    
    `vault-add` commands does much processing depending on the vault type even
    before the request is forwarded to remote server. Since default values for
    parameters are now filled only on server side, the client-side logic would
    fail if the vault type was not explicitly given. In this case we have to
    retrieve and use the default vault type from schema.
    
    https://fedorahosted.org/freeipa/ticket/6047
    
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>