fix multi threading issues

[JohnHeikens]

• the packet retreiver should wait until we disconnect due to some reason.
• the client should process incoming packets while there are packets left, and wait on the packet retreiver if there are none.
• the renderer should wait on the client to finish processing before starting another render call. (done already)

[JohnHeikens]

also, the retreiver should not keep waiting if nothing is coming. in that case, it should disconnect.