test: remove unused args and comparison fix

Remove unused arguments and change non-strict comparison
to the strict one in test.

PR-URL: #11396
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/internet/test-dgram-multicast-multi-process.js

@@ -21,14 +21,14 @@ if (common.inFreeBSDJail) {
   return;
 }
 
-function launchChildProcess(index) {
+function launchChildProcess() {
   const worker = fork(__filename, ['child']);
   workers[worker.pid] = worker;
 
   worker.messagesReceived = [];
 
   // Handle the death of workers.
-  worker.on('exit', function(code, signal) {
+  worker.on('exit', function(code) {
     // Don't consider this the true death if the worker has finished
     // successfully or if the exit code is 0.
     if (worker.isDone || code === 0) {
@@ -188,7 +188,7 @@ if (process.argv[2] === 'child') {
 
       process.send({ message: buf.toString() });
 
-      if (receivedMessages.length == messages.length) {
+      if (receivedMessages.length === messages.length) {
         // .dropMembership() not strictly needed but here as a sanity check.
         listenSocket.dropMembership(LOCAL_BROADCAST_HOST);
         process.nextTick(function() {