title: localstack error for IoT: Connection was closed before we received a valid response
body: <p>I am trying to setup localstack for our AWS IoT stack testing. But I am getting connection timeout error for very basic API such as <code>list-thing-groups</code>, <code>list-thing</code>, etc. As IoT is not supported in the free tier, I am using the paid version of the localstack. I have enabled SQS, SNS and IoT services using localstack by setting up the variable <code>SERVICES</code></p>
  
  <pre><code>export SERVICES=sqs,sns,iot
  </code></pre>
  
  <p>Getting the following error message:</p>
  
  <pre><code>$ aws --endpoint-url=http://localhost:4589 iot list-thing-groups
  Connection was closed before we received a valid response from endpoint URL: "http://localhost:4589/thing-groups".
  </code></pre>
  
  <p>When I tried to use SNS, it worked fine without any issue. Not sure why it is not working for IoT. The message after starting the localstack container does not talk about IoT, not sure why.</p>
  
  <pre><code>Starting local dev environment. CTRL-C to quit.
  2019-11-07T01:37:24:INFO:localstack_ext.bootstrap.licensing: Successfully activated API key
  Waiting for all LocalStack services to be ready
  Starting mock SNS (http port 4575)...
  2019-11-07T01:37:25:INFO:localstack.multiserver: Starting multi API server process on port 51492
  Starting mock SQS (http port 4576)...
  Ready.
  </code></pre>
  
  <p>Let me know if I am missing anything.</p>