refactor: adjust server endpoint in hub kubeconfig template (#603)

## What type of PR is this?

/kind refactor

## What this PR does / why we need it:

Adjust server endpoint from `karpor-server.karpor.svc` to `127.0.0.1` in
hub cluster kubeconfig template, becuase the k8s internal domain cannot
be resolved in the local environment.

## Which issue(s) this PR fixes:

Fixes #520

pkg/util/certgenerator/generator.go

@@ -28,11 +28,11 @@ import (
 	"k8s.io/client-go/util/keyutil"
 )
 
-const kubeConfigTemplate = `apiVersion: v1
+const hubClusterKubeConfigTemplate = `apiVersion: v1
 clusters:
 - cluster:
     insecure-skip-tls-verify: true
-    server: https://karpor-server.%s.svc:7443
+    server: https://127.0.0.1:7443
   name: karpor
 contexts:
 - context:
@@ -189,5 +189,5 @@ func generateAdminKubeconfig(namespace string, cert *x509.Certificate, key crypt
 	if err != nil {
 		return "", fmt.Errorf("unable to marshal private key to PEM %s", err)
 	}
-	return fmt.Sprintf(kubeConfigTemplate, namespace, base64.StdEncoding.EncodeToString(certData), base64.StdEncoding.EncodeToString(keyData)), nil
+	return fmt.Sprintf(hubClusterKubeConfigTemplate, base64.StdEncoding.EncodeToString(certData), base64.StdEncoding.EncodeToString(keyData)), nil
 }