Lock to docker 1.7.0, fix ecs tcs mounts

After docker 1.7.0 we (Remind) have seen this issue pop up:

moby/moby#13914

Now that this is closed:

moby/moby#16001

We can use the new docker-engine packages, but with an old version. I'm
moving the empire_ami back to docker 1.7.0 till 13914 above is fixed.

As well, this should fix ECS stats - we just needed a bunch of volumes,
per:

aws/amazon-ecs-agent#174

Doing this internally @ Remind fixed this.

ansible/roles/aws_ecs/files/etc/init/ecs_agent.conf

@@ -20,7 +20,7 @@ pre-start script
     fi
 end script
 
-exec /usr/bin/docker run --name ecs-agent --env-file=/etc/empire/env/ecs_agent.env -v /var/run/ecs_agent:/data -v /var/run/docker.sock:/var/run/docker.sock -v /var/log/ecs:/log -p 127.0.0.1:51678:51678 $IMAGE
+exec /usr/bin/docker run --name ecs-agent --env-file=/etc/empire/env/ecs_agent.env -v /var/run/ecs_agent:/data -v /var/run/docker.sock:/var/run/docker.sock -v /var/log/ecs:/log -v /var/run/docker/execdriver:/var/lib/docker/execdriver:ro -v /sys/fs/cgroup:/sys/fs/cgroup:ro -p 127.0.0.1:51678:51678 $IMAGE
 
 post-stop script
     /usr/bin/docker stop -t 2 ecs-agent || true

ansible/roles/docker/tasks/main.yml

@@ -38,7 +38,7 @@
 - apt: name=apparmor
   tags: 
     - build_ami
-- apt: name=docker-engine
+- apt: name=docker-engine=1.7.0-0~trusty
   tags: 
     - build_ami