Add enableExecuteCommand for ECS service in blue-green-container-deployment

[rogperez]

We've recently needed to debug live containers and have had to use this procedure to do it. https://docs.aws.amazon.com/AmazonECS/latest/developerguide/ecs-exec.html

We've decided to make it a permanent change to our services but were prohibited from updating our services directly with this new field. Therefore we've needed to modify the custom resource directly.