ECS: Render Taskless Services

[2opremio]

Right now (after #2026) we only "discover" ECS services through tasks (we obtain the task list from Docker labels and obtain services associated to those tasks, the process is well documented in #2065).

This means we don't obtain information nor render services without associated tasks (e.g. Services with replication factor 0, which is valid, and services whose tasks are not running).

This may or may not be a real problem for users.

[2opremio]

I think that a regular call to ListServices wouldn't add a lot of overhead considering we regularly call DescribeService for every service.

[ekimekim]

Well, as of #2065 we only describe services that have tasks running on our machine. I like this because it means the number of calls is bounded by the number of things running per machine, whereas describing every service on every machine would be problematic in very large clusters.
Sigh. These rate limits make everything difficult.

Given the current constraints we may need to accept not supporting showing non-running services for now.
Ideally we should document that somewhere.