[UPDATE] SteamCMD and CSGO guides

[nmelehan]

Updated these two guides:

1. Install SteamCMD for a Steam Game Server
   /docs/game-servers/install-steamcmd-for-a-steam-game-server/

   Updated in place.

2. Launch a Counter Strike: Global Offensive (CS:GO) server on Ubuntu 14.04
   /docs/game-servers/launch-a-counter-strike-global-offensive-server-on-ubuntu-14-04/

   Created a new Ubuntu 18.04 guide at /docs/game-servers/launch-a-counter-strike-global-offensive-server-on-ubuntu-18-04/ and set a deprecated link from the old guide.

The SteamCMD guide had some incorrect firewall rules. Here's what the output from netstat was when running the CS:GO game server:

sudo netstat -plntu
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.1:27015         0.0.0.0:*               LISTEN      1587/./srcds_linux
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      582/systemd-resolve
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      702/sshd
tcp6       0      0 :::22                   :::*                    LISTEN      702/sshd
udp        0      0 127.0.0.53:53           0.0.0.0:*                           582/systemd-resolve
udp        0      0 0.0.0.0:27005           0.0.0.0:*                           1587/./srcds_linux
udp        0      0 0.0.0.0:27015           0.0.0.0:*                           1587/./srcds_linux
udp        0      0 0.0.0.0:27020           0.0.0.0:*                           1587/./srcds_linux

The game server is listening on ports between 2700 and 27030. The old SteamCMD and CS:GO guides listed those ports as the source ports:

-A INPUT -p udp -m udp --sport 27000:27030 --dport 1025:65355 -j ACCEPT
-A INPUT -p udp -m udp --sport 4380 --dport 1025:65355 -j ACCEPT

Really, they should be the destination ports in the firewall. Trying to connect to the game server with the existing rules from the guides failed. Switching the rules to use the relevant ports as the destination ports succeeded.

This brings into question whether any other game guides that also link to the SteamCMD guide will work under either the old version of the guide or this new version. I will create a separate card/task for reviewing those guides.

In the meantime, these guide updates require another tech/copy edit from someone else.

[nmelehan]

Tech Edit - Launch a Counter Strike Global Offensive server on Ubuntu 14.04