archive: use reference counting for archive+input

Make the input_stream implementation hold a reference on the
archive_file object.  Allow the caller to "close" the archive_file
object immediately, no matter if the open_stream() method has
succeeded or not.

src/input/archive_input_plugin.c

@@ -67,12 +67,9 @@ input_archive_open(struct input_stream *is, const char *pathname,
 
 	//setup fileops
 	opened = archive_file_open_stream(file, is, filename, error_r);
+	archive_file_close(file);
 	g_free(pname);
 
-	if (!opened) {
-		archive_file_close(file);
-	}
-
 	return opened;
 }