title: When I building docker image, why multiple-choice question was skiped? (ex. gographic area by installing dnsutils)
body: <p>I created a simple Dockerfile and run <code>docker build .</code></p>
  <pre><code>FROM ubuntu
  RUN apt-get update &amp;&amp; apt-get -y install dnsutils
  </code></pre>
  <p>I expected that this build will fail because automatically installing would not be able to answer the multiple-choice questions. However, the process used uninitialized value and build succeeded.</p>
  <pre><code>Please select the geographic area in which you live. Subsequent configuration
  questions will narrow this down by presenting a list of cities, representing
  the time zones in which they are located.
  
    1. Africa      4. Australia  7. Atlantic  10. Pacific  13. Etc
    2. America     5. Arctic     8. Europe    11. SystemV
    3. Antarctica  6. Asia       9. Indian    12. US
  Geographic area: 
  Use of uninitialized value $_[1] in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 111.
  </code></pre>
  <p>Why can ubuntu skip it? In other word, can I skip this question at manually installing?</p>