Enable awsvpc network mode for ECS services and tasks and
their underlying task definitions
Improve test suite to thoroughly test the changes
Use runme.sh technique to run old and new versions of botocore to
ensure that the modules work with older botocore and older network modes
and fail gracefully if awsvpc network mode is used with older botocore
Tests for:
* ecs_cluster
* ecs_service
* ecs_service_facts
* ecs_taskdefinition
* ecs_taskdefinition_facts
* Add idempotency testing
Test ecs_cluster, ecs_service and ecs_taskdefinition for trivial
idempotency. Add FIXMEs to the tests because the latter two fail.
Remove unused dependencies