test: fix parallel/test-net-socket-local-address

Fix flakiness where the client sometimes closed the server before the
server had the chance to process the outstanding client connection.
Make the server close itself instead.

Fixes: nodejs#2475

test/parallel/parallel.status

@@ -21,4 +21,3 @@ test-child-process-exit-code : PASS,FLAKY
 [$system==solaris] # Also applies to SmartOS
 
 [$system==freebsd]
-test-net-socket-local-address : PASS,FLAKY

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

@@ -15,23 +15,21 @@ var serverRemotePorts = [];
 
 const server = net.createServer(function(socket) {
  serverRemotePorts.push(socket.remotePort);
- conns++;
+ if (++conns === 2) this.close();
 });
 
 const client = new net.Socket();
 
-server.on('close', common.mustCall(function() {
+process.on('exit', function() {
  assert.deepEqual(clientLocalPorts, serverRemotePorts,
  'client and server should agree on the ports used');
  assert.equal(2, conns);
-}));
+});
 
 server.listen(common.PORT, common.localhostIPv4, testConnect);
 
 function testConnect() {
- if (conns == 2) {
- return server.close();
- }
+ if (conns >= 2) return;
  client.connect(common.PORT, common.localhostIPv4, function() {
  clientLocalPorts.push(this.localPort);
  this.once('close', testConnect);