Fix server shut down on exit.

If there's a websocket being waited on the shut down won't actually
happen. Add a new event for shut down and send it to break the websocket
out of its loop.

game/server/server.py

@@ -6,8 +6,10 @@ from threading import Thread
 import uvicorn
 from uvicorn import Config
 
+from game.server import EventStream
 from game.server.app import app
 from game.server.settings import ServerSettings
+from game.sim import GameUpdateEvents
 
 
 class Server(uvicorn.Server):
@@ -34,4 +36,5 @@ class Server(uvicorn.Server):
             yield
         finally:
             self.should_exit = True
+            EventStream.put_nowait(GameUpdateEvents().shut_down())
             thread.join()