Set delimiter so that the CommonPrefixes response can properly be determined

Signed-off-by: Julius Härtl <jus@bitgrid.net>

Author: juliusknorr

apps/files_external/lib/Lib/Storage/AmazonS3.php

@@ -163,6 +163,7 @@ private function doesDirectoryExist($path) {
 					'Bucket' => $this->bucket,
 					'Prefix' => rtrim($path, '/'),
 					'MaxKeys' => 1,
+					'Delimiter' => '/',
 				]);
 				$this->directoryCache[$path] =
 					$result['Contents'][0]['Key'] === rtrim($path, '/') . '/'  ||