test: fix flaky test-http-client-timeout-event

Race condition caused occasional failure on CI. Chained callbacks used
to remove race condition.

PR-URL: https://github.com/nodejs/node/pull/10293
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-http-client-timeout-event.js

@@ -1,33 +1,30 @@
 'use strict';
 const common = require('../common');
-const assert = require('assert');
 const http = require('http');
 
-var options = {
+const options = {
   method: 'GET',
   port: undefined,
   host: '127.0.0.1',
   path: '/'
 };
 
-var server = http.createServer();
+const server = http.createServer();
 
 server.listen(0, options.host, function() {
   options.port = this.address().port;
-  var req = http.request(options);
+  const req = http.request(options);
   req.on('error', function() {
     // this space is intentionally left blank
   });
   req.on('close', common.mustCall(() => server.close()));
 
-  var timeout_events = 0;
   req.setTimeout(1);
-  req.on('timeout', common.mustCall(() => timeout_events += 1));
-  setTimeout(function() {
-    req.destroy();
-    assert.strictEqual(timeout_events, 1);
-  }, common.platformTimeout(100));
-  setTimeout(function() {
-    req.end();
-  }, common.platformTimeout(50));
+  req.on('timeout', common.mustCall(() => {
+    req.end(() => {
+      setTimeout(() => {
+        req.destroy();
+      }, 100);
+    });
+  }));
 });