ctrl: Fix fd leak in ctrl_listen()

Use the same pattern for handling rtnl_listen() errors that
is used across other iproute2 commands. All other commands
exit with status of 2 if rtnl_listen fails.

Reported-off-by: Maks Mishin <maks.mishinFZ@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

genl/ctrl.c

@@ -334,8 +334,9 @@ static int ctrl_listen(int argc, char **argv)
 	}
 
 	if (rtnl_listen(&rth, print_ctrl, (void *) stdout) < 0)
-		return -1;
+		exit(2);
-
+	
+	rtnl_close(&rth);	
 	return 0;
 }