return path of tmp file like filestorage/common does. Fixes broken folder-/multifile-download.

lib/filesystemview.php

@@ -282,7 +282,8 @@ class OC_FilesystemView {
 			if($source){
 				$extention=substr($path,strrpos($path,'.'));
 				$tmpFile=OC_Helper::tmpFile($extention);
-				return file_put_contents($tmpFile,$source);
+				file_put_contents($tmpFile,$source);
+				return $tmpFile;
 			}
 		}
 	}