http: don't cork noop .end()

Calling .end() a second time should be a noop and not
leave the socket corked.

Fixes: #36620

Author: ronag

lib/_http_outgoing.js

@@ -810,17 +810,18 @@ OutgoingMessage.prototype.end = function end(chunk, encoding, callback) {
     encoding = null;
   }
 
-  if (this.socket) {
-    this.socket.cork();
-  }
-
   if (chunk) {
     if (this.finished) {
       onError(this,
               new ERR_STREAM_WRITE_AFTER_END(),
               typeof callback !== 'function' ? nop : callback);
       return this;
     }
+
+    if (this.socket) {
+      this.socket.cork();
+    }
+
     write_(this, chunk, encoding, null, true);
   } else if (this.finished) {
     if (typeof callback === 'function') {

test/parallel/test-http-outgoing-end-multiple.js

@@ -9,10 +9,13 @@ const onWriteAfterEndError = common.mustCall((err) => {
 
 const server = http.createServer(common.mustCall(function(req, res) {
   res.end('testing ended state', common.mustCall());
+  assert.strictEqual(res.writableCorked, 0);
   res.end(common.mustCall((err) => {
     assert.strictEqual(err.code, 'ERR_STREAM_ALREADY_FINISHED');
   }));
+  assert.strictEqual(res.writableCorked, 0);
   res.end('end', onWriteAfterEndError);
+  assert.strictEqual(res.writableCorked, 0);
   res.on('error', onWriteAfterEndError);
   res.on('finish', common.mustCall(() => {
     res.end(common.mustCall((err) => {