Restrict functions and structs that aren't used outside of the

nodecontroller to have package private scope. This makes reasoning
about the code in this package much simpler.

pkg/cloudprovider/plugins.go

@@ -39,8 +39,7 @@ var providers = make(map[string]Factory)
 func RegisterCloudProvider(name string, cloud Factory) {
 	providersMutex.Lock()
 	defer providersMutex.Unlock()
-	_, found := providers[name]
-	if found {
+	if _, found := providers[name]; found {
 		glog.Fatalf("Cloud provider %q was registered twice", name)
 	}
 	glog.V(1).Infof("Registered cloud provider %q", name)