Track client connections and autostop server add-ons when all clients leave

Reviewed By: mweststrate

Differential Revision: D34045584

fbshipit-source-id: 1ad0cfffb9d304f0359c973d76d6956f7e932f72

desktop/flipper-server-core/src/comms/ServerController.tsx

@@ -510,6 +510,7 @@ export class ServerController
       );
       this.flipperServer.emit('client-disconnected', {id});
       this.connections.delete(id);
+      this.flipperServer.pluginManager.stopAllServerAddOns(id);
     }
   }
 }