add option to disable background scanning of files

when using (only) object store this job doesn't do any scanning anyway,
but all the setup can still be expensive on large setups

Signed-off-by: Robin Appelman <robin@icewind.nl>

apps/files/lib/BackgroundJob/ScanFiles.php

@@ -97,6 +97,10 @@ class ScanFiles extends \OC\BackgroundJob\TimedJob {
 	 * @throws \Exception
 	 */
 	protected function run($argument) {
+		if ($this->config->getSystemValueBool('files_no_background_scan', false)) {
+			return;
+		}
+		
 		$offset = $this->config->getAppValue('files', 'cronjob_scan_files', 0);
 		$users = $this->userManager->search('', self::USERS_PER_SESSION, $offset);
 		if (!count($users)) {