Cleanup the old configuration file of the cluster (#256)

Signed-off-by: icbc-yangcheng <shineus1996@gmail.com>

hack/create-cluster.sh

@@ -26,6 +26,11 @@ if [[ -z "${KUBECONFIG}" ]]; then
   exit 1
 fi
 
+if [ -f "${KUBECONFIG}" ];then
+  echo "Removing old kubeconfig file."
+  rm -f ${KUBECONFIG}
+fi
+
 kind create cluster --name "${CLUSTER_NAME}" --kubeconfig="${KUBECONFIG}" --wait=120s
 
 # Kind cluster's context name contains a "kind-" prefix by default.