[test_node_factory.cpp] Remove unused unordered_map include.

It was causing problems compiling on OpenSolaris (no joke!):
http://www.cpantesters.org/cpan/report/4c2ebc04-d934-11e2-9caf-ce73a3ac3ce9
Merge pull request #123 from caldwell/fix_opensolaris

Yeah, that's an old file that I was using during development ... thanks for the patch!

[test_node_factory.cpp] Remove unused unordered_map include.