cluster: remove obsolete array allocation

The array was only used to create a key. Instead of allocating that
first, just directly create the necessary string.

PR-URL: #20567
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

lib/internal/cluster/master.js

@@ -275,12 +275,8 @@ function queryServer(worker, message) {
   if (worker.exitedAfterDisconnect)
     return;
 
-  const args = [message.address,
-                message.port,
-                message.addressType,
-                message.fd,
-                message.index];
-  const key = args.join(':');
+  const key = `${message.address}:${message.port}:${message.addressType}:` +
+              `${message.fd}:${message.index}`;
   var handle = handles[key];
 
   if (handle === undefined) {