Use common controller/store for httpTriggerSet and functionReferenceResolver (#390)

This fixes a bug where functionReferenceResolver returned out-of-date function metadata and caused the router to proxy requests to old function pods.

It also uses the go context package to shutdown the controller when the router is shutting down.

router/functionReferenceResolver.go

@@ -36,8 +36,6 @@ type (
 	// functionReferenceResolver provides a resolver to turn a function
 	// reference into a resolveResult
 	functionReferenceResolver struct {
-		fissionClient *crd.FissionClient
-
 		// FunctionReference -> function metadata
 		refCache *cache.Cache
 
@@ -68,28 +66,14 @@ const (
 	resolveResultSingleFunction = iota
 )
 
-func makeFunctionReferenceResolver(fissionClient *crd.FissionClient) *functionReferenceResolver {
+func makeFunctionReferenceResolver(store k8sCache.Store) *functionReferenceResolver {
 	frr := &functionReferenceResolver{
-		fissionClient: fissionClient,
-		refCache:      cache.MakeCache(time.Minute, 0),
+		refCache: cache.MakeCache(time.Minute, 0),
+		store:    store,
 	}
 	return frr
 }
 
-// Sync starts syncing crd function resources from k8s api server
-func (frr *functionReferenceResolver) Sync(crdClient *rest.RESTClient) {
-	stopCh := make(chan struct{})
-	store, controller := makeK8SCache(crdClient)
-	frr.stopCh = stopCh
-	frr.store = store
-	go controller.Run(stopCh)
-}
-
-// Stop stops crd resources syncing
-func (frr *functionReferenceResolver) Stop() {
-	frr.stopCh <- struct{}{}
-}
-
 func makeK8SCache(crdClient *rest.RESTClient) (k8sCache.Store, k8sCache.Controller) {
 	watchlist := k8sCache.NewListWatchFromClient(crdClient, "functions", metav1.NamespaceDefault, fields.Everything())
 	listWatch := &k8sCache.ListWatch{