title: Chef knife plugin(s) not recognized?
body: <p>I have chef-client v11.12.2. I installed the knife-block and knife-playground plugins via Gemfile, and see that they're installed.</p>
  
  <pre><code>&gt; bundle install
  .....
  Using knife-block (0.1.1)
  Using knife-playground (0.2.2)
  Using knife-spork (1.3.4)
  ......
  
  &gt; bundle show knife-block
  /opt/chef-server/embedded/lib/ruby/gems/1.9.1/gems/knife-block-0.1.1
  </code></pre>
  
  <p>However I get this when I do a knife block list, for example. Same issue for knife pg command. What else am I missing?</p>
  
  <pre><code>&gt; knife block list
  FATAL: Cannot find sub command for: 'block list'
  </code></pre>