In the case where a node_version is less than what's in the distro,
we'll wind up installing distro packages instead of upstream packages
which will either fail due to binary path naming issues, or succeed but
install a different version of nodejs than was requested.
Pin the package to the nodesource repo.
Put the file in as a template, as we should really update this role to
be able to optionally make use of a local mirror, in which case the file
will need to jinja.
Change-Id: If313d895a73bd2be7f598179a51b6485a37000ba
45fe96382b