use protobuf content type instead of json for k8s client (#131)

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**What does this PR do / Why do we need it**:

This MR is a part of effort to elevate single eks cluster performance by
migrating the EKS components to use protobuf instead of json.

Modify kubeconfig type to use content type
application/vnd.kubernetes.protobuf instead of json for performance
gain.

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cmd/main.go

@@ -78,7 +78,16 @@ func main() {
 		setupLog.Error(err, "unable to build REST config")
 		os.Exit(1)
 	}
-	clientSet, err := kubernetes.NewForConfig(restCFG)
+
+	clientSetRestConfig, err := config.BuildRestConfig(controllerCFG.RuntimeConfig)
+	if err != nil {
+		setupLog.Error(err, "unable to build REST config")
+		os.Exit(1)
+	}
+	clientSetRestConfig.AcceptContentTypes = "application/vnd.kubernetes.protobuf,application/json"
+	clientSetRestConfig.ContentType = "application/vnd.kubernetes.protobuf"
+
+	clientSet, err := kubernetes.NewForConfig(clientSetRestConfig)
 	if err != nil {
 		setupLog.Error(err, "unable to obtain clientSet")
 		os.Exit(1)