test: fix flaky http-server-keep-alive-timeout

Make sure the connection is not closed until the 3 requests and the
`timeout` event are received.
Some code refactoring to avoid duplicated code.

Fixes: #20013
PR-URL: #20093
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

test/parallel/test-http-server-keep-alive-timeout.js

@@ -18,15 +18,28 @@ function run() {
   if (fn) fn(run);
 }
 
-test(function serverEndKeepAliveTimeoutWithPipeline(cb) {
+function done(server, socket, cb) {
+  socket.destroy();
+  server.close(cb);
+}
+
+function serverTest(withPipeline, cb) {
+  let gotAll = false;
+  let timedout = false;
   const server = http.createServer(common.mustCall((req, res) => {
-    res.end();
+    if (withPipeline)
+      res.end();
+    if (req.url === '/3') {
+      gotAll = true;
+      if (timedout)
+        done(server, req.socket, cb);
+    }
   }, 3));
-  server.setTimeout(500, common.mustCall((socket) => {
+  server.setTimeout(500, common.mustCallAtLeast((socket) => {
     // End this test and call `run()` for the next test (if any).
-    socket.destroy();
-    server.close();
-    cb();
+    timedout = true;
+    if (gotAll)
+      done(server, socket, cb);
   }));
   server.keepAliveTimeout = 50;
   server.listen(0, common.mustCall(() => {
@@ -40,26 +53,12 @@ test(function serverEndKeepAliveTimeoutWithPipeline(cb) {
       c.write('GET /3 HTTP/1.1\r\nHost: localhost\r\n\r\n');
     });
   }));
+}
+
+test(function serverEndKeepAliveTimeoutWithPipeline(cb) {
+  serverTest(true, cb);
 });
 
 test(function serverNoEndKeepAliveTimeoutWithPipeline(cb) {
-  const server = http.createServer(common.mustCall(3));
-  server.setTimeout(500, common.mustCall((socket) => {
-    // End this test and call `run()` for the next test (if any).
-    socket.destroy();
-    server.close();
-    cb();
-  }));
-  server.keepAliveTimeout = 50;
-  server.listen(0, common.mustCall(() => {
-    const options = {
-      port: server.address().port,
-      allowHalfOpen: true
-    };
-    const c = net.connect(options, () => {
-      c.write('GET /1 HTTP/1.1\r\nHost: localhost\r\n\r\n');
-      c.write('GET /2 HTTP/1.1\r\nHost: localhost\r\n\r\n');
-      c.write('GET /3 HTTP/1.1\r\nHost: localhost\r\n\r\n');
-    });
-  }));
+  serverTest(false, cb);
 });