Use the upstream dind package to run docker

It is pretty close to our docker package, if we adjust the command
that is run to avoid the actual dind startup script. We can't use
the normal docker image as it does not have mkfs and so on.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

test/cases/030_security/000_docker-bench/test-docker-bench.yml

@@ -24,10 +24,9 @@ services:
   - name: dhcpcd
     image: linuxkit/dhcpcd:4b7b8bb024cebb1bbb9c8026d44d7cbc8e202c41
   - name: docker
-    image: linuxkit/docker-ce:9b937df179bdbebbc70243779978057df0b54190
+    image: docker:17.06.0-ce-dind
     capabilities:
      - all
-    net: host
     mounts:
      - type: cgroup
        options: ["rw","nosuid","noexec","nodev","relatime"]
@@ -35,6 +34,7 @@ services:
      - /var/lib/docker:/var/lib/docker
      - /lib/modules:/lib/modules
      - /run:/var/run
+    command: ["/usr/local/bin/docker-init", "/usr/local/bin/dockerd"]
   - name: test-docker-bench
     image: linuxkit/test-docker-bench:4999d3484771e8466580c0dc2e479595e49faa85
     ipc: host