Avoid flicking of backup target list if default changes

dashboard/src/views/BackupTargetsView.vue

@@ -134,7 +134,8 @@ async function onPrimaryTargetChanged(value) {
   const [error] = await backupTargetsModel.setPrimary(value);
   if (error) return console.error(error);
 
-  await refresh();
+  // update the list to be in sync without flickering
+  targets.value.forEach(t => t.primary = t.id === value);
 
   primaryTargetId.value = value;
   primaryTargetChangeBusy.value = false;