add variables support for user_data helper

If you have a template with two ec2 resources, and they can largely
share a templatized userdata script, but need to pass different
variables to it so they can render slightly differently, is there a
way to do this?

In our case we basically have two ec2 nodes in the same cf template,
and we want to have a common user-data lono template that we pass a
chef role to.

I guess if user_data had the ability to pass variables like partials,
it would do the trick? However, I do wonder if you can call the same
partial twice in the same template?