Use -L flag in curl

The cirros image uses a redirect.  Use curl -L to follow redirections.

Change-Id: I3a9309901ab3528442009fd6802600c51c98242f

tools/start

@@ -49,7 +49,7 @@ docker-compose -f ./compose/nova-compute-network.yml up -d
 IMAGE_URL=http://download.cirros-cloud.net/0.3.3/
 IMAGE=cirros-0.3.3-x86_64-disk.img
 if ! [ -f "$IMAGE" ]; then
-    curl -o ./$IMAGE $IMAGE_URL/$IMAGE
+    curl -L -o ./$IMAGE $IMAGE_URL/$IMAGE
 fi
 
 until keystone user-list | grep glance