Fix: make kubernetes token string optional for ApiConfig

Change-Id: I679944fb5df3ed71a8af7c12a92aec3c4e36bee6
diff --git a/apps/k8s-node/app/src/main/java/org/onosproject/k8snode/util/K8sNodeUtil.java b/apps/k8s-node/app/src/main/java/org/onosproject/k8snode/util/K8sNodeUtil.java
index 023cec9..bf76feb 100644
--- a/apps/k8s-node/app/src/main/java/org/onosproject/k8snode/util/K8sNodeUtil.java
+++ b/apps/k8s-node/app/src/main/java/org/onosproject/k8snode/util/K8sNodeUtil.java
@@ -248,10 +248,13 @@
 
         if (config.scheme() == K8sApiConfig.Scheme.HTTPS) {
             configBuilder.withTrustCerts(true)
-                    .withOauthToken(config.token())
                     .withCaCertData(config.caCertData())
                     .withClientCertData(config.clientCertData())
                     .withClientKeyData(config.clientKeyData());
+
+            if (StringUtils.isNotEmpty(config.token())) {
+                configBuilder.withOauthToken(config.token());
+            }
         }
 
         return new DefaultKubernetesClient(configBuilder.build());