[ECS] [BUG]: Tasks in deactivating state do not show up on container instance tasks

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**Tell us about your request**
ECS tasks stopped due to load balancer health check failure enter "deactivating" state. Our load balancer deregistration delay is 30min which seems to be the time until containers are actually removed.

During that time they do not show up on the container instance and ECS will try to schedule new tasks on that instance. The tasks will keep failing to provision due to insufficient resources.

**Which service(s) is this request for?**
ECS

No files, tests, or code entry points are named. Start by examining ECS behavior for tasks in the "deactivating" state after a load balancer health-check failure and the 30-minute deregistration delay; done means those tasks appear on the container instance and resource-based scheduling no longer attempts to overcommit it.

Written by the indexing model from the issue text.