net: persist net.Socket options before connect

Remembers net.Socket options called before connect and retroactively
applies them after the handle has been created.

This change makes the following function calls more user-friendly:

- setKeepAlive()
- setNoDelay()
- ref()
- unref()

Related: https://github.com/joyent/node/issues/7077 and
https://github.com/joyent/node/issues/8572

Fixes: https://github.com/joyent/node/issues/7077
Fixes: https://github.com/joyent/node/issues/8572
PR-URL: https://github.com/nodejs/io.js/pull/1518


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Roman Reiss <me@silverwind.io>