Mesos containerizer to support docker credential helpers for private docker registries

In Pinterest, we use Amazon ECR as our docker registry and use https://github.com/awslabs/amazon-ecr-credential-helper to let docker engine to get auth token automatically.

It works well with docker containerizer, as long as I have the .docker/config.json configured "credStores" and --docker_config configured for mesos-agent.

However, this doesn't work for mesos containerizer. Meanwhile we want to use mesos containerizer's GPU support, so we have to run a separate docker registry on http and without auth, purely for mesos containerizer.

I think it will be good if mesos containerizer can support https://github.com/docker/docker-credential-helpers by default, so that it will address a pain point for the users who are using crendential helpers with private registries on ECR, GCR, quay, dockerhub etc.

This might be related to MESOS-7088

CC jieyu gilbert