Integration test insecure registry

The integrations tests use their own registry so avoid hitting docker
hub rate limits.

This was using a self signed certificate but instead use
`--insecure-registry` to let the docker daemon use HTTP.

test/integration/docker/vm/Dockerfile

@@ -5,7 +5,6 @@ WORKDIR /work
 RUN apt-get update --fix-missing && apt-get -y install openssh-client openssh-server docker.io
 
 RUN mkdir /root/.ssh && ln -s /shared/ssh/id_rsa.pub /root/.ssh/authorized_keys
-RUN mkdir -p /etc/docker/certs.d/registry:4443 && ln -s /shared/certs/domain.crt /etc/docker/certs.d/registry:4443/ca.crt
 
 RUN echo "HOST_TOKEN=abcd" >> /etc/environment