http: fixes memory retention issue with FreeList and HTTPParser

Fixes: https://github.com/nodejs/node/issues/29394
Refs: https://github.com/nodejs/node/pull/33167#issuecomment-622102450

PR-URL: https://github.com/nodejs/node/pull/33190


Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>