Avoid using an undocumented version of net.connect

I had assumed net.connect had the same signatures as tls.connect;
specifically, the

    net.connect(port, host, options, callback)

form. However, this only works by coincidence (can you spot it?
https://github.com/joyent/node/blob/0882a7506394e07ae6564ccf3db401b8fb7f7071/lib/net.js#L86).

To avoid that, I'm now using the `connect(options, callback) form that
`tls` and `net` have in common.