Improve logging (#10069)

The default is "" which is not clearly seen in the log. This makes it
better.

Change-Id: Idc8fc192c69d30ea93ad1cc05a68738028f89506

pkg/reconciler/autoscaling/kpa/scaler.go

@@ -320,7 +320,8 @@ func (ks *scaler) scale(ctx context.Context, pa *pav1alpha1.PodAutoscaler, sks *
 
 	min, max := pa.ScaleBounds(asConfig)
 	initialScale := kparesources.GetInitialScale(asConfig, pa)
-	logger.Debugf("MinScale = %d, MaxScale = %d, InitialScale = %d, DesiredScale = %d Reachable = %v",
+	// Log reachability as quoted string, since default value is "".
+	logger.Debugf("MinScale = %d, MaxScale = %d, InitialScale = %d, DesiredScale = %d Reachable = %q",
 		min, max, initialScale, desiredScale, pa.Spec.Reachability)
 	// If initial scale has been attained, ignore the initialScale altogether.
 	if initialScale > 1 && !pa.Status.IsScaleTargetInitialized() {