Update Dockerfile (#51)
Update Dockerfile (#51)

Adding docker support.
Existing docker base image already supports [this](https://github.com/googleapis/testing-infra-docker/pull/10)
Require for Cloud AI repo [ai-platform-samples]
(https://github.com/GoogleCloudPlatform/ai-platform-samples/blob/master/training/pytorch/structured/custom_containers/base/scripts/train-local.sh#L38)

googleapis/testing-infra-docker