test: smaller chunk size for smaller person.jpg

PR-URL: https://github.com/nodejs/node/pull/5813


Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rod Vagg <rod@vagg.org>

Conflicts:
	test/parallel/test-zlib-params.js