title: Unable to list kafka topics in openwhisk setup
body: <p>Setup details: 
  I am setting up openwhisk on my local ubuntu(16.04) vm. in this setup kafka is running in one docker and zookeeper in another docker.</p>
  
  <p>I connect to the the kafka docker using cmd </p>
  
  <pre><code>sudo docker exec -it &lt;container id&gt; sh
  </code></pre>
  
  <p>once connected i execute the following command to get the list of topics</p>
  
  <pre><code>bin/kafka-topics.sh --list --zookeeper localhost:2181
  </code></pre>
  
  <p>which gives me an exception</p>
  
  <pre><code>Error: Exception thrown by the agent : java.rmi.server.ExportException: Port already in use: 7203; nested exception is:
          java.net.BindException: Address already in use
  </code></pre>
  
  <p>i am unable to understand why is it trying to use 7203 port?</p>
  
  <p>docker ps output</p>
  
  <pre><code>83eba3961247        ches/kafka:0.10.0.1              "/start.sh"              
  11 days ago         Up 23 hours         7203/tcp, 0.0.0.0:9092-&gt;9092/tcp                                                                                                                       
  kafka
  947fa689a7ef        zookeeper:3.4                    "/docker-
  entrypoin..."   11 days ago         Up 23 hours         2888/tcp, 
  0.0.0.0:2181-&gt;2181/tcp, 3888/tcp                                                                                                             zookeeper
  </code></pre>