Fix endless loop on windows servers

Directory seperator is \ on windows
However we can just check for path != dirname(path) because that is
the same for '' (empty string), '.' and DIRECTORY_SEPARATOR on all OS

apps/files_sharing/lib/helper.php

@@ -125,7 +125,7 @@ class Helper {
 
 
 		$ids = array();
-		while ($path !== '' && $path !== '.' && $path !== '/') {
+		while ($path !== dirname($path)) {
 			$info = $ownerView->getFileInfo($path);
 			if ($info instanceof \OC\Files\FileInfo) {
 				$ids[] = $info['fileid'];

apps/files_sharing/lib/updater.php

@@ -38,7 +38,7 @@ class Shared_Updater {
 		\OC\Files\Filesystem::initMountPoints($user);
 		$view = new \OC\Files\View('/' . $user);
 		if ($view->file_exists($path)) {
-			while ($path !== '/') {
+			while ($path !== dirname($path)) {
 				$etag = $view->getETag($path);
 				$view->putFileInfo($path, array('etag' => $etag));
 				$path = dirname($path);