Don't render machine name if not applicable to step

Dependencies

• [2] TX7Q4RAS Add page showing latest build steps
• [3] 24BMQDZA Start of single-process hydra-queue-runner
• [4] 2GUAKGTB Fix indentation of build.tt
• [5] PH3DFCNU Render machine correctly if it doesn't contain @
• [*] J5UVLXOK * Start of a basic Catalyst web interface.

Change contents

• replacement in src/root/build.tt at line 48
  [3.932]→[2.884:958](∅→∅)
  − <td>[% INCLUDE renderMachineName machine=step.machine %]</td>
  [3.932]

  [3.985]
  + <td>[% IF step.busy == 1 || step.status == 0 || step.status == 1 || step.status == 4 || step.status == 7; INCLUDE renderMachineName machine=step.machine; ELSE; "<em>n/a</em>"; END %]</td>