Amazon ColumnStore AMI support of IAM role with certificates

The current version of the AMI requires that a user have the acess/secret key certificates in files on the Instance them's. The Amazon IAM role is there to allow the user to define these types of certificates which would allow the runing process to access them without have to have them locally in a file on the system..

So the logic in postConfigure and the MCS cloud scripts need to change to allow the use of ENV variables, which is what would be passed from the AIM setup.