title: Unable to add build step in jenkins job
body: <p>I was able to create the new job but I am NOT able to add any build step.
  This behaviour is reproducible and it occurs when I try to do it from the initial “configure” page I get after job creation  as well as with a later configure attempt. And its persists for all job types.
   It does not depend on whether I am logged in or not.
   The problem is that when I open the “add build step” I get a selection of possible job types (“shell script”, “windows batch”, …) but when I select one of those nothing more happens.
   I also have other jobs of this type already up and running and I am also not able to add more build steps to those.</p>