title: Unknown Redis command called from Lua script
body: <p>I try to use "config get" command  to get one of redis status metrics in lua ,but get "Unknown Redis command called from Lua script", I do not know why?</p>
  
  <pre><code>127.0.0.1:6379&gt; eval "return redis.call('config get','lazyfree_pending_objects')" 0
  (error) ERR Error running script (call to f_4e7351811a87a6961eb6fe85622dce826bbc681c): @user_script:1: @user_script: 1: Unknown Redis command called from Lua script
  127.0.0.1:6379&gt; eval "return redis.call('config', 'get','lazyfree_pending_objects')" 0
  (empty list or set)
  127.0.0.1:6379&gt; eval "return redis.call('config', 'get','used_memory_dataset')" 0
  (empty list or set)
  127.0.0.1:6379&gt; eval "return redis.call('config', 'get used_memory_dataset')" 0
  (error) ERR Error running script (call to f_25423fef37dc24142677d59a564f5b664f9e0f45): @user_script:1: ERR CONFIG subcommand must be one of GET, SET, RESETSTAT, REWRITE
  </code></pre>