This fixes the CONNECT/Upgrade HTTP functionality, which was not getting
sliced properly, because readable wasn't emitted on this tick.
Conflicts:
test/simple/test-http-connect.js
With Upgrade or CONNECT request, http.ClientRequest emits 'close' event
after its socket is closed. However, after receiving a response, the socket
is not under management by the request.
http.ClientRequest should detach the socket before 'upgrade'/'connect'
event is emitted to pass the socket to a user. After that, it should
emit 'close' event immediately without waiting for closing of the socket.
Fixes#2510.