Resolve issue of Backup tool not correctly detecting .maintenance.flag

Author: hiren0241

app/code/Magento/Backup/Controller/Adminhtml/Index/Create.php

@@ -55,7 +55,9 @@ public function execute()
             $this->_coreRegistry->register('backup_manager', $backupManager);
 
             if ($this->getRequest()->getParam('maintenance_mode')) {
-                if (!$this->maintenanceMode->set(true)) {
+                $this->maintenanceMode->set(true);
+
+                if (!$this->maintenanceMode->isOn()) {
                     $response->setError(
                         __(
                             'You need more permissions to activate maintenance mode right now.'