title: Jenkins : delete workspace on slave too
body: <p>I have a job with configuration matrix to perform build on 2 computer (master and slave).
  I have "Delete workspace before build starts" option checked on this job.</p>
  
  <p>Unfortunately, workspace is delete only on "master" node, that is node where main job (job which launch all the job necessary to cover configuration matrix) is perform.</p>
  
  <p>Workspace on second node is not delete.</p>
  
  <p>I think it's a Jenkins error : because job has configuration matrix, there is a master job to launch other job. So "Delete workspace before build starts" option is apply only for this master job. I think this option should be apply for all matrix configuration job.</p>
  
  <p>Someone know if I wrong ?</p>