Required attributes

Newly created nodes and nodes reloaded from source control through knife won't have data populated from ohai yet.  Using 'unknown' as the values for os_family, machine, platform, and platform_version allows rundeck to interact with the node (potentially kicking off chef-client and therefore ohai).  

If the fqdn is not set, the node name is the only chance for connecting to the machine.  This won't be good enough in some environments.