api/v1beta1: use go-dockerclient instead of docker-api-structs

This involves updating go-dockerclient and removing the patched code.

I haven't ran the end-to-end tests, just ``hack/test-go.sh`` and ``hack/test-integration.sh``, and both pass. Can anybody confirm that everything is ok?

Related to #692 and fsouza/go-dockerclient#146.