https://github.com/OpenRA/OpenRA/issues/2564

fixed a issue with pinging Master-server

Sometimes initial TickCount is less than zero, so (Environment.TickCount - lastPing) can be less than "MasterPingInterval * 1000". That's why PingMasterServer() is not calling for a long time until somebody connected.
Merge pull request #2684 from xaionaro/bleed

fixed a issue with pinging Master-server