test: fix worker send error

In test-child-process-fork-closed-channel-segfault.js, race condition
is observed between the server getting closed and the worker sending
a message. Accommodate the potential errors.

Earlier, the same race was observed between the client and server
and was addressed through ignoring the relevant errors through error
handler. The same mechanism is re-used for worker too.

The only difference is that the filter is applied at the callback
instead of at the worker's error listener.

Refs: #3635 (comment)
Fixes: #20836
PR-URL: #20973

Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Jon Moss <[email protected]>
Reviewed-By: Matheus Marchini <[email protected]>
Reviewed-By: Joyee Cheung <[email protected]>
Reviewed-By: Bartosz Sosnowski <[email protected]>

test/parallel/test-child-process-fork-closed-channel-segfault.js

@@ -31,6 +31,16 @@ const server = net
   .listen(0, function() {
     const worker = cluster.fork();
 
+    worker.on('error', function(err) {
+      if (
+        err.code !== 'ECONNRESET' &&
+        err.code !== 'ECONNREFUSED' &&
+        err.code !== 'EMFILE'
+      ) {
+        throw err;
+      }
+    });
+
     function send(callback) {
       const s = net.connect(server.address().port, function() {
         worker.send({}, s, callback);
@@ -66,7 +76,10 @@ const server = net
         send(function(err) {
           // Ignore errors when sending the second handle because the worker
           // may already have exited.
-          if (err && err.code !== 'ERR_IPC_CHANNEL_CLOSED') {
+          if (err && err.code !== 'ERR_IPC_CHANNEL_CLOSED' &&
+                     err.code !== 'ECONNRESET' &&
+                     err.code !== 'ECONNREFUSED' &&
+                     err.code !== 'EMFILE') {
             throw err;
           }
         });