test: fix flaky test-net-socket-local-address

test-net-socket-local-address had a race condition that resulted in
unreliability on FreeBSD and Windows. This changes fixes the issue.

Fixes: #2475
PR-URL: #4109
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>

test/parallel/parallel.status

@@ -22,4 +22,3 @@ test-child-process-exit-code         : PASS,FLAKY
 test-debug-signal-cluster         : PASS,FLAKY
 
 [$system==freebsd]
-test-net-socket-local-address     : PASS,FLAKY

test/parallel/test-net-socket-local-address.js

@@ -15,7 +15,7 @@ var serverRemotePorts = [];
 
 const server = net.createServer(function(socket) {
   serverRemotePorts.push(socket.remotePort);
-  conns++;
+  testConnect();
 });
 
 const client = new net.Socket();
@@ -29,12 +29,18 @@ server.on('close', common.mustCall(function() {
 server.listen(common.PORT, common.localhostIPv4, testConnect);
 
 function testConnect() {
-  if (conns == 2) {
+  if (conns > serverRemotePorts.length || conns > clientLocalPorts.length) {
+    // We're waiting for a callback to fire.
+    return;
+  }
+
+  if (conns === 2) {
     return server.close();
   }
   client.connect(common.PORT, common.localhostIPv4, function() {
     clientLocalPorts.push(this.localPort);
     this.once('close', testConnect);
     this.destroy();
   });
+  conns++;
 }