http: clean up HttpParser correctly

Remove reference to kOnMessageBegin from HttpParser
to avoid leaking Server instances in FreeList.

PR-URL: #39292
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>

lib/_http_common.js

@@ -45,6 +45,7 @@ let debug = require('internal/util/debuglog').debuglog('http', (fn) => {
 
 const kIncomingMessage = Symbol('IncomingMessage');
 const kRequestTimeout = Symbol('RequestTimeout');
+const kOnMessageBegin = HTTPParser.kOnMessageBegin | 0;
 const kOnHeaders = HTTPParser.kOnHeaders | 0;
 const kOnHeadersComplete = HTTPParser.kOnHeadersComplete | 0;
 const kOnBody = HTTPParser.kOnBody | 0;
@@ -238,6 +239,7 @@ function cleanParser(parser) {
  parser.incoming = null;
  parser.outgoing = null;
  parser.maxHeaderPairs = MAX_HEADER_PAIRS;
+ parser[kOnMessageBegin] = null;
  parser[kOnExecute] = null;
  parser[kOnTimeout] = null;
  parser._consumed = false;