podvm: Set shutdown behavior for aws packer image creation

to prevent leaving stopped VMs if Packer execution is unexpectedly interrupted
see: https://developer.hashicorp.com/packer/integrations/hashicorp/amazon/latest/components/builder/ebs#run-configuration

Signed-off-by: Snir Sheriber <ssheribe@redhat.com>

src/cloud-api-adaptor/aws/image/rhel/aws-rhel.pkr.hcl

@@ -30,7 +30,8 @@ source "amazon-ebs" "rhel" {
     volume_size           = "${var.volume_size}"
   }
 
-  ssh_username = "ec2-user"
+  ssh_username      = "ec2-user"
+  shutdown_behavior = "terminate"
 }
 
 build {