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/boot.sh

@@ -4,6 +4,6 @@ while [ ! -f /root/.ssh/authorized_keys ]; do echo "Waiting for ssh keys"; sleep
 
 service ssh restart
 
-dockerd --max-concurrent-downloads 1 &
+dockerd --max-concurrent-downloads 1 --insecure-registry registry:4443 &
 
 exec sleep infinity