A fix for no method ssh_identity_file with in Irfonfan::DSL::EC2

[rottmanj]

Refs #347

I didn't add any tests as there were never any to begin with for the DSL.

[westbywest]

This appears to resolve the problem described in #347 for bootstrap, but kick and ssh still are not able to connect to EC2 instance without adding command line option -i knife/credentials/realm-cluster.pem.

Indeed, I commented out the ssh_identity_file method after running bootstrap on an instance, and didn't receive the error "no method ssh_identity_file" when trying knife cluster kick, suggesting that method was not even executed.

[westbywest]

Following up, it looks like identity_file and ssh_user are not getting included into the session by configure_session method in Chef::Knife::ClusterSsh. The commit below demonstrates a crude hack to simply insert identity_file and ssh_user of the first computer in the target list. This lets "knife cluster ssh", "knife cluster kick", etc work cluster-wide w/o having to pass -x and -i options, but it will not work realm-wide.
https://github.com/splicemachine/ironfan/commit/554a077d5de2b368671c2918c9827ce0b2f9d171