Fix monitoring setup script.

Remove the firewall rule created for monitoring as part of kube-down.
Reuse master auth for Grafana.

cluster/rackspace/util.sh

@@ -327,6 +327,10 @@ function setup-monitoring {
     echo "TODO"
 }
 
+function teardown-monitoring {
+  echo "TODO"
+}
+
 # Perform preparations required to run e2e tests
 function prepare-e2e() {
   echo "Rackspace doesn't need special preparations for e2e tests"