Use Task group to filter on list tasks instead of StartedBy

[yinshiua]

closes #97

Testing

$ make build

$ make test

Tasks:

$ ecs-cli compose up

$ ecs-cli compose ps
// Shows the correct task IDs (does not include the ones started by service)

Service:

$ ecs-cli compose service up

$ ecs-cli compose service ps
// Shows the correct task IDs

[aaithal]

Looks mostly good. I have a small comment. Can you also confirm that Tasks that have already been started using the "started by" field continue to show up with this change?

[aaithal]

1. Can you use a const for comparison instead of "task"? Also, it'd make more sense for EntityType() to return an enum instead of a string (https://github.com/aws/amazon-ecs-cli/blob/master/ecs-cli/modules/cli/compose/entity/entity.go#L42)

2. Can you update the comment for CollectTasksWithStatus to reflect this change as well? Right now, filterLocal is only mentioned in the context of startedBy

[aaithal]

this can just be type. enitity.entityType stutters.

[yinshiua]

type is used in go, don't think I can name it as type, but I can name it as types. What do you think? Right now is entityType.Type, but with the change it'll be types.EntityType

[aaithal]

types is fine. You can just name it types.Type ?

[yinshiua]

yes, I've tested using running ecs-cli compose up with the old cli and run ecs-cli compose ps with the change.