Enhancement for aws_iam_role

[rx294]

Ref chef-boneyard#174 from https://github.com/chef/inspec-aws
Please consider the following features to support cis-aws-foundations-1.18
Enhancements:

  describe aws_iam_role(IAM_MASTER_ROLE_NAME) do
    it { should exist }
    its('inline-policies') { should include IAM_MASTER_INLINE_POLICY }
    its('attached-policies') { should include IAM_MASTER_ATTACHED_POLICY }
  end

1. List inline policies
   aws iam list-role-policies --role-name <role_name>
2. List attached policlies
   aws iam list-attached-role-policies --role-name <rolename>