http: socket connection timeout for http request

This allows passing the socket connection timeout to http#request
such that it will be set before the socket is connecting

PR-URL: https://github.com/nodejs/node/pull/8101
Fixes: https://github.com/nodejs/node/issues/7580


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>