fix being told youre afk twice if you use /afk before the timer runs out

src/aoclient.cpp

@@ -324,6 +324,7 @@ Server* AOClient::getServer() { return server; }
 
 void AOClient::onAfkTimeout()
 {
+    if (!is_afk)
         sendServerMessage("You are now AFK.");
     is_afk = true;
 }