YARN needs a modern version of NodeJS and if we don't use the role
to get the latest version, we end up failing on most platforms that
ship an old version of it.
This patch also adds testing to validate that ensure-yarn alone works.
Co-Authored-By: Andreas Jaeger <aj@suse.com>
Change-Id: I83ac09bc5751c85c6f1eac550d289a300ca2255e