Fixed EMR's describe_cluster_command

There's two bugs being fixed in this command:
* It should be Ec2InstanceAttributes rather than EC2InstanceAttributes according to the docs and what's returned by the API (http://docs.aws.amazon.com/ElasticMapReduce/latest/API/API_Cluster.html)
* Parsed Applications weren't being returned which was confusing the parser, and causing some data to go missing.