test: fix EPIPE on Windows

Refactor test-cluster-shared-leak.js to remove flakiness on Windows.

Fixes: nodejs#3956
PR-URL: nodejs#4173

Author: Trott

test/parallel/parallel.status

@@ -9,7 +9,6 @@ prefix parallel
 [$system==win32]
 test-child-process-fork-regr-gh-2847 : PASS,FLAKY
 test-cluster-net-send                : PASS,FLAKY
-test-cluster-shared-leak             : PASS,FLAKY
 test-tls-ticket-cluster              : PASS,FLAKY
 
 [$system==linux]

test/parallel/test-cluster-shared-leak.js

@@ -15,15 +15,16 @@ if (cluster.isMaster) {
   worker1 = cluster.fork();
   worker1.on('message', common.mustCall(function() {
     worker2 = cluster.fork();
+    // make sure worker2 is listening before doing anything else
     conn = net.connect(common.PORT, common.mustCall(function() {
       worker1.send('die');
-      worker2.send('die');
     }));
     conn.on('error', function(e) {
       // ECONNRESET is OK
       if (e.code !== 'ECONNRESET')
         throw e;
     });
+    worker2.send('die');
   }));
 
   cluster.on('exit', function(worker, exitCode, signalCode) {