net: emit host in lookup event

Previously, we emitted ip and addressType. This change includes the host
as the last argument to the lookup event.

PR-URL: https://github.com/nodejs/node/pull/5598


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>