Stop using dockerfile/* images

As per
http://blog.docker.com/2015/03/updates-available-to-popular-repos-update-your-images/
docker has stopped answering dockerfile/redis and dockerfile/nginx.  Fix all
users in our tree.  Sadly this means a lot of published examples are now broken.

cmd/integration/integration.go

@@ -1075,7 +1075,7 @@ const (
 			"containers": [
 				{
 					"name": "redis",
-					"image": "dockerfile/redis",
+					"image": "redis",
 					"volumeMounts": [{
 						"name": "redis-data",
 						"mountPath": "/data"
@@ -1103,7 +1103,7 @@ const (
 id: container-vm-guestbook-manifest
 containers:
   - name: redis
-    image: dockerfile/redis
+    image: redis
     volumeMounts:
       - name: redis-data
         mountPath: /data