feature(main): using up and down interface

Signed-off-by: cuisongliu <cuisongliu@qq.com>

pkg/runtime/runtime.go

@@ -94,13 +94,13 @@ func (k *KubeadmRuntime) Reset() error {
 	return k.reset()
 }
 func (k *KubeadmRuntime) ScaleUp(newMasterIPList []string, newNodeIPList []string) error {
-	if newMasterIPList != nil && len(newMasterIPList) != 0 {
+	if len(newMasterIPList) != 0 {
 		logger.Info("%s will be added as master", newMasterIPList)
 		if err := k.joinMasters(newMasterIPList); err != nil {
 			return err
 		}
 	}
-	if newNodeIPList != nil && len(newNodeIPList) != 0 {
+	if len(newNodeIPList) != 0 {
 		logger.Info("%s will be added as worker", newNodeIPList)
 		if err := k.joinNodes(newNodeIPList); err != nil {
 			return err
@@ -111,13 +111,13 @@ func (k *KubeadmRuntime) ScaleUp(newMasterIPList []string, newNodeIPList []strin
 }
 
 func (k *KubeadmRuntime) ScaleDown(deleteMastersIPList []string, deleteNodesIPList []string) error {
-	if deleteMastersIPList != nil && len(deleteMastersIPList) != 0 {
+	if len(deleteMastersIPList) != 0 {
 		logger.Info("master %s will be deleted", deleteMastersIPList)
 		if err := k.deleteMasters(deleteMastersIPList); err != nil {
 			return err
 		}
 	}
-	if deleteNodesIPList != nil && len(deleteNodesIPList) != 0 {
+	if len(deleteNodesIPList) != 0 {
 		logger.Info("worker %s will be deleted", deleteNodesIPList)
 		return k.deleteNodes(deleteNodesIPList)
 	}