Update sdk to v1.7.0rc0 #402

Job	Run time
Publish Image (pytorch-dist-sendrecv-test, examples/pytorch/smoke-dist/Dockerfile) / Publish Image	51s
Publish Image (pytorch-elastic-example-echo, examples/pytorch/elastic/echo/Dockerfile) / Publish Image	19s
Publish Image (pytorch-elastic-example-imagenet, examples/pytorch/elastic/imagenet/Dockerfile) / Publish Image	4m 44s
Publish Image (tf-dist-mnist-test, examples/tensorflow/dist-mnist/Dockerfile) / Publish Image	51s
Publish Image (tf-distributed-worker, examples/tensorflow/distribution_strategy/estimator-API/Doc... / Publish Image	53s
Publish Image (tf-multi-worker-strategy, examples/tensorflow/distribution_strategy/keras-API/Dock... / Publish Image	3m 11s
Publish Image (tf-mnist-with-summaries, examples/tensorflow/mnist_with_summaries/Dockerfile) / Publish Image	33s
Publish Image (tf-smoke, examples/tensorflow/tf_sample/Dockerfile) / Publish Image	46s
	12m 8s

Provide feedback