test: fix broken FreeBSD test

Fixes net-server-max-connections-close-makes-more-available
Handles connection 'error' event so the test ends.

PR-URL: https://github.com/nodejs/io.js/pull/1881


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Brendan Ashworth <brendan.ashworth@me.com>