http_parser: use `MakeCallback`

Make `HTTPParser` an instance of `AsyncWrap` and make it use
`MakeCallback`. This means that async wrap hooks will be called on
consumed TCP sockets as well as on non-consumed ones.

Additional uses of `AsyncCallbackScope` are necessary to prevent
improper state from progressing that triggers failure in the
test-http-pipeline-flood.js test. Optimally this wouldn't be necessary,
but for the time being it's the most sure way to allow operations to
proceed as they have.

Fix: https://github.com/nodejs/node/issues/4416
PR-URL: https://github.com/nodejs/node/pull/5419


Reviewed-By: Fedor Indutny <fedor@indutny.com>