Change certificateAutority function signature

This function only care about the kubeconfig file path, not the whole
clusterConfig obj, It will allow us to reuse this function and also
add the test around it.

pkg/crc/machine/kubeconfig.go

@@ -62,7 +62,7 @@ func WriteKubeconfig(ip string, clusterConfig *ClusterConfig) error {
 	// Make sure .kube/config exist if not then this will create
 	_, _ = os.OpenFile(kubeconfig, os.O_RDONLY|os.O_CREATE, 0600)
 
-	ca, err := certificateAuthority(clusterConfig)
+	ca, err := certificateAuthority(clusterConfig.KubeConfig)
 	if err != nil {
 		return err
 	}
@@ -94,8 +94,8 @@ func WriteKubeconfig(ip string, clusterConfig *ClusterConfig) error {
 	return clientcmd.WriteToFile(*cfg, kubeconfig)
 }
 
-func certificateAuthority(clusterConfig *ClusterConfig) ([]byte, error) {
-	bin, err := ioutil.ReadFile(clusterConfig.KubeConfig)
+func certificateAuthority(kubeconfigFile string) ([]byte, error) {
+	bin, err := ioutil.ReadFile(kubeconfigFile)
 	if err != nil {
 		return nil, err
 	}
@@ -105,7 +105,7 @@ func certificateAuthority(clusterConfig *ClusterConfig) ([]byte, error) {
 	}
 	cluster, ok := builtin.Clusters["crc"]
 	if !ok {
-		return nil, fmt.Errorf("crc cluster not found in kubeconfig %s", clusterConfig.KubeConfig)
+		return nil, fmt.Errorf("crc cluster not found in kubeconfig %s", kubeconfigFile)
 	}
 	return cluster.CertificateAuthorityData, nil
 }