Update to use an Amazon Linux 2 image - WISCALERTS-2

• In order to increase disk space allocated for Docker container utilize Amazon Linux 2. By default Amazon Linux 2 uses overlay2 storage driver, which gives the base storage size of the space left on the disk.
• Removed SSM agent as it's shipped with all Amazon Linux 2 AMIs.
• Utilized SSM param store for storing IICS user credentials.
• Increased EBS volume size to allocate more disk space.

@JARED.KOSANOVIC @ERIC.SCHOVILLE @jont

terraform/ecs.tf

@@ -28,7 +28,7 @@ resource "aws_iam_role" "ecs-task-execution" {
     {
       "Action": "sts:AssumeRole",
       "Principal": {
-        "Service": "ecs.amazonaws.com"
+        "Service": "ecs-tasks.amazonaws.com"
       },
       "Effect":"Allow"
     }