Add hooks from ASG to drain container instances

[simplesteph]

https://aws.amazon.com/blogs/compute/how-to-automate-container-instance-draining-in-amazon-ecs/

[simplesteph]

not relevant as draining an instance won't necessarily mean the tasks are removed from it. This is manual and the steps are:

• mark your instance as drained
• scale down your ecs service, your tasks shut down correctly.
• remove the instance from your asg