include AWS IAM role-name in ec2 plugin data

[kcbraunschweig]

Describe the Enhancement

Currently the ohai ec2 plugin reads from the AWS metadata service but strips out all IAM data to prevent leaking security credentials:
https://github.com/chef/ohai/blob/master/lib/ohai/plugins/ec2.rb#L123-L127

We should modify this slightly to still include the IAM role-name which is part of the metadata at:
iam/security-credentials/role-name
see: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instancedata-data-categories.html
Don't include the data returned in the document under role-name as that includes actually includes credentials, but the name from the URL path should be fine.

Describe the Need

The role assigned to the host provides its identity and is likely to be used to make decisions about how to configure it.

Current Alternative

Currently this could be found in recipe code by either making http calls to the metadata service during the run and parsing the response, or including the ruby aws sdk as a library can calling STS GetCallerIdentity which includes role information.

Can We Help You Implement This?

This is a simple modification to the scope of the filtering based on the data already present. Creating an issue in case someone gets to it before me.