BUG/MINOR: tools: fix off-by-one in port size check

port_to_str() checks that the port size is at least 5 characters instead
of at least 6. While in theory it could permit a buffer overflow, it's
harmless because all callers have at least 6 characters here.

This fix needs to be backported to 1.7, 1.6 and 1.5.

src/standard.c

@@ -1409,7 +1409,7 @@ int port_to_str(struct sockaddr_storage *addr, char *str, int size)
 	uint16_t port;
 
 
-	if (size < 5)
+	if (size < 6)
 		return 0;
 	*str = '\0';