test: fix test-net-settimeout flakiness

Wait for the data to be received by the socket before creating the
clean-up timer. This way, a possible (though unlikely) `ECONNRESET`
error can be avoided.

PR-URL: #6166
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

test/parallel/test-net-settimeout.js

@@ -8,22 +8,24 @@ const assert = require('assert');
 
 const T = 100;
 
-const server = net.createServer(function(c) {
+const server = net.createServer(common.mustCall((c) => {
   c.write('hello');
-});
+}));
+
 server.listen(common.PORT);
 
 const socket = net.createConnection(common.PORT, 'localhost');
 
-const s = socket.setTimeout(T, function() {
+const s = socket.setTimeout(T, () => {
   common.fail('Socket timeout event is not expected to fire');
 });
 assert.ok(s instanceof net.Socket);
 
-socket.setTimeout(0);
-
-setTimeout(function() {
-  socket.destroy();
-  server.close();
-}, T * 2);
+socket.on('data', common.mustCall(() => {
+  setTimeout(function() {
+    socket.destroy();
+    server.close();
+  }, T * 2);
+}));
 
+socket.setTimeout(0);