Make cmdq->client_exit a tristate (-1 means "not set") so that if explicitly

set it can be copied from child to parent cmdq by if-shell and
source-file. This fixes using attach or new. From Chris Johnsen.

cmd-source-file.c

@@ -95,6 +95,9 @@ cmd_source_file_done(struct cmd_q *cmdq1)
 {
 	struct cmd_q	*cmdq = cmdq1->data;
 
+	if (cmdq1->client_exit >= 0)
+		cmdq->client_exit = cmdq1->client_exit;
+
 	cmdq_free(cmdq1);
 
 	cfg_references--;