test: enable featureGate AddMetrics on kube-apiserver testserver

Author: aaron-prindle

cmd/kube-apiserver/app/testing/testserver.go

@@ -194,6 +194,7 @@ func StartTestServer(t ktesting.TB, instanceOptions *TestServerInstanceOptions,
 	fs := pflag.NewFlagSet("test", pflag.PanicOnError)
 
 	featureGate := utilfeature.DefaultMutableFeatureGate
+	featureGate.AddMetrics()
 	effectiveVersion := utilversion.DefaultKubeEffectiveVersion()
 	if instanceOptions.BinaryVersion != "" {
 		effectiveVersion = utilversion.NewEffectiveVersion(instanceOptions.BinaryVersion)