Setup eventing extension sugar controller (#920)

We'll need sugar controller for reconciling broker for tests
 which labels namespace and annotates the triggers.

 Currently, sugar controller is not part of the eventing nightly release setup
 by test-infra libs. This changeset adds install of same for nightly
 CI setup.

test/common.sh

@@ -36,6 +36,11 @@ function knative_setup() {
 
   if [ "${eventing_version}" = "latest" ]; then
     start_latest_knative_eventing
+
+    # install the sugar controller
+    kubectl apply --filename https://storage.googleapis.com/knative-nightly/eventing/latest/eventing-sugar-controller.yaml
+    wait_until_pods_running knative-eventing || return 1
+
   else
     start_release_knative_eventing "${eventing_version}"
   fi