Create cluster with encrypted root volumes

The following steps let you create a cluster using instances with encrypted root volumes.

1. Create a custom AMI choosing one of the first two methods described in the official doc here:
   • Modify an AWS ParallelCluster AMI
   • Build a Custom AWS ParallelCluster AMI
2. Copy the AMI to a new one using encryption, as described here
3. Use the new encrypted AMI ID as custom_ami parameter value in ParallelCluster configuration file
4. Create the cluster