That's a good question. It seems that cargo should take care of that for you, but I guess I see why they don't do it since you would need to tell it about HTTP ports or JMX ports to query.
The easiest way I can think of is to write a simple JUnit (not JSFUnit) test. In that test, ping your HTTP port to find out if JBoss is running. Since HtmlUnit is already there, I would use that. Let that run during the normal test phase and set a flag somewhere. When you hit cargo in the integration-test phase it would look at the flag and know if JBoss is running or not. I don't know the details of the implementation, but that's the best approach I can think of.