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

@@ -46,6 +46,7 @@ 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;
@@ -239,6 +240,7 @@ 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;