degesch: fix confusing message

It seemed like we were connecting albeit we were connected already.

degesch.c

@@ -4969,7 +4969,8 @@ static void
 on_irc_ping_timeout (void *user_data)
 {
 	struct server *s = user_data;
-	log_server_error (s, s->buffer, "Connection timeout");
+	log_server_error (s, s->buffer,
+		"%s: %s", "Disconnected from server", "timeout");
 	irc_disconnect (s);
 }