title: Mqtt Client Paho close issue (Java)
body: <p>I have:</p>
  
  <pre><code>MqttAsyncClient mq;
     ...
     mq = new MqttAsyncClient(myServer1,"app1");
     mq.connect();
     ...
     //(1)
     //doing something with mq (pub/sub)
     ...
     mq.disconnect();
     mq.close();
     //(2)
  </code></pre>
  
  <p>Now I am using a Monitoring Console and I see:</p>
  
  <ul>
  <li>In (1), 3 Mqtt threads:
  MQTT REC, MQTT SND and MQTT Call</li>
  <li>In (2), 2 Mqtt threads:
  MQTT SND and MQTT Call</li>
  <li>After further seconds only 1 thread
  MQTT CALL</li>
  </ul>
  
  <p>The CALL thread will never be stopped. 
  How come ?</p>