genRpcClient = function(app, opts) {
  opts.context = app;
  opts.routeContext = app;
  if(!!opts.rpcClient) {
    return opts.rpcClient.create(opts);
  } else {
    return Client.create(opts);
  }
}
Generate rpc client

@param {Object} app current application context
@param {Object} opts contructor parameters for rpc client
@return {Object} rpc client