title: composer-rest-server Unhandled 'error' event
body: <p>When I try <code>composer-rest-server -c acme-admin@test-bna</code> I get this output:</p>
  
  <pre><code>Discovering the Returning Transactions..
  Discovered types from business network definition
  Generating schemas for all types in business network definition ...
  Generated schemas for all types in business network definition
  Adding schemas for all types to Loopback ...
  Added schemas for all types to Loopback
  events.js:183
        throw er; // Unhandled 'error' event
        ^
  
  Error: listen EADDRINUSE :::3000
      at Server.setupListenHandle [as _listen2] (net.js:1360:14)
      at listenInCluster (net.js:1401:12)
      at Server.listen (net.js:1485:7)
      at module.exports.promise.then.then (/usr/local/lib/node_modules/composer-rest-server/cli.js:143:19)
      at &lt;anonymous&gt;
      at process._tickCallback (internal/process/next_tick.js:189:7)
  </code></pre>
  
  <p>I am actually doing a udemy course about how to setup a hyperledger multi org network. </p>