Avoids scanning the root storage

This check will skip the background scan for the root storage
because there is nothing in the root storage that isn't already
in another (mostly user-) storage.

Fixes #22501

lib/private/files/utils/scanner.php

@@ -119,6 +119,10 @@ class Scanner extends PublicEmitter {
 			if (is_null($mount->getStorage())) {
 				continue;
 			}
+			// don't scan the root storage
+			if ($mount->getStorage()->instanceOfStorage('\OC\Files\Storage\Local') && $mount->getMountPoint() === '/') {
+				continue;
+			}
 			$scanner = $mount->getStorage()->getScanner();
 			$this->attachListener($mount);
 			$scanner->backgroundScan();