Sample controller: Init flags

Without this, the flags to make klog log to stdout are not even shown.
Figuring out the `InitFlags()` is not very intuitive for ppl new to the
project, which is the target audience of the sample-controller.

staging/src/k8s.io/sample-controller/main.go

@@ -38,6 +38,7 @@ var (
 )
 
 func main() {
+	klog.InitFlags(nil)
 	flag.Parse()
 
 	// set up signals so we handle the first shutdown signal gracefully