Fix exception being thrown on changelevel

[AnAkkk]

This fixes the problem described in koraktor/steam-condenser#270

[koraktor]

Finally back at this problem…

Doesn’t this make the RCONTerminator workaround obsolete?

[AnAkkk]

I don't think it would, the RCONTerminator will still be sent after a successful reply. It just won't throw the exception if there haven't been any reply.
I've been using this fix since I've posted it, and everything works fine, I haven't had any more issues.

[AnAkkk]

FYI it's now even worse on Dota 2 Reborn (Source 2), Valve changed a bit the rcon code apparently, the workaround no longer works and steam condenser just throw a timeout exception every time as the server won't reply to the 2nd packet.