D16963: Fix running kdoctools-install autotest without kdoctools installed

[Ralf Habacker]

habacker added a reviewer: aacid.

REPOSITORY
  R238 KDocTools

REVISION DETAIL
  https://phabricator.kde.org/D16963

To: habacker, aacid
Cc: kde-frameworks-devel, kde-doc-english, michaelh, ngraham, bruns, skadinna