dont use the mtimes stored in zip archives since they dont update correctly

lib/archive/zip.php

@@ -74,8 +74,7 @@ class OC_Archive_ZIP extends OC_Archive{
 	 * @return int
 	 */
 	function mtime($path){
-		$stat=$this->zip->statName($path);
-		return $stat['mtime'];
+		return filemtime($this->path);
 	}
 	/**
 	 * get the files in a folder