test: improve test-net-server-pause-on-connect

Previously the test had a massive timeout (3s!), reduce this to a
platform specific timeout of 50ms.

This test runs two servers at the same time in an attempt to compare
behaviour. I've added a check to make sure one event fires before the
other event, as is expected, but that is a possible race condition.

Improves test run time on my machine from 0m3.141s to 0m0.356s.

PR-URL: https://github.com/nodejs/node/pull/2429


Reviewed-By: Rich Trott <rtrott@gmail.com>