test: move broadcast/multicast test to internet/

Move parallel/test-dgram-broadcast-multi-process to test/internet.

The test does not play nice with firewalls that restrict broadcast
or multicast traffic, nor can it be rewritten to use only loopback
traffic without running into platform-specific limitations, see also
commits 52e600a9 and 236533c (TODO: update second one before landing.)

PR-URL: https://github.com/iojs/io.js/pull/259


Reviewed-By: Rod Vagg <rod@vagg.org>