Move async work out of the Server constructor

Summary:
I feel like doing async stuff here isn't a good idea in general.
But more pressingly, it means you can't immediately call server.close() after new Server(), because the things to close haven't been created yet.

Reviewed By: danielbuechele

Differential Revision: D10488301

fbshipit-source-id: 76ebe91e0c09f353e0bdb9f2e4116757e757abb2

src/dispatcher/server.js

@@ -13,6 +13,7 @@ import type Client from '../Client.js';
 
 export default (store: Store, logger: Logger) => {
   const server = new Server(logger, store);
+  server.init();
 
   server.addListener('new-client', (client: Client) => {
     store.dispatch({