test: fix flaky http-client-timeout-agent

Close the connection immediately after receiving the `end` event to
avoid that the `timeout` event is fired before the connection closes
gracefully.
Move the test back to parallel.
PR-URL: #19856Fixes: #19804
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

Author: santigimeno

…ential/test-http-client-timeout-agent.js …rallel/test-http-client-timeout-agent.jstest/sequential/test-http-client-timeout-agent.js renamed to test/parallel/test-http-client-timeout-agent.js test/sequential/test-http-client-timeout-agent.js renamed to test/parallel/test-http-client-timeout-agent.js

@@ -48,11 +48,10 @@ const server = http.createServer(function(req, res) {
 
 server.listen(0,options.host,function(){
 options.port=this.address().port;
-letreq;
 
 for(requests_sent=0;requests_sent<30;requests_sent+=1){
 options.path=`/${requests_sent}`;
-req=http.request(options);
+constreq=http.request(options);
 req.id=requests_sent;
 req.on('response',function(res){
 res.on('data',function(data){
@@ -61,6 +60,7 @@ server.listen(0, options.host, function() {
 res.on('end',function(data){
 console.log(`res#${this.req.id} end`);
 requests_done+=1;
+req.destroy();
 });
 });
 req.on('close',function(){