Makes a lot of entity systems unsubscribe from events on shutdown.

Content.Server/GameObjects/EntitySystems/GhostRoleSystem.cs

@@ -30,9 +30,18 @@ namespace Content.Server.GameObjects.EntitySystems
 
         public override void Initialize()
         {
+            base.Initialize();
+
             SubscribeLocalEvent<PlayerAttachSystemMessage>(OnPlayerAttached);
         }
 
+        public override void Shutdown()
+        {
+            base.Shutdown();
+
+            UnsubscribeLocalEvent<PlayerAttachSystemMessage>();
+        }
+
         private uint GetNextRoleIdentifier()
         {
             return unchecked(_nextRoleIdentifier++);