test: fix process.title expectation

`process.title` would work properly only in FreeBSD, OSX, and Linux as
per test/parallel/test-setproctitle.js.

This patch makes sure that the test expects an empty string in other
platforms.

This patch helps fix the SmartOS failures in
https://ci.nodejs.org/job/node-test-commit/6962/ for
https://github.com/nodejs/node/pull/10456

PR-URL: https://github.com/nodejs/node/pull/10597


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>