this fixes a race condition where if 2 goroutines try to send a packet at the same time, they could end up being
malformed due to the 2 separate calls to peer.conn.Write().
instead of writing the packet size to peer.conn.Write() directly, we make space in buf for the packet size,
and patch it in place. this lets us get away with only having 1 call to peer.conn.Write() which will ensure that
the full packet is written properly and be goroutine safe :3
- the shard's ip sent to the client via the login server is currently hardcoded in config/config.go
- no packets other than P_CL2FE_REQ_PC_ENTER and P_CL2FE_REQ_PC_LOADING_COMPLETE are supported via the shard server