Bug 16174: icondirectories.t broken due to bug 15527

 Bug 16174: icondirectories.t broken due to bug 15527

This patch fixes it.

To test:
- Run
  $ prove xt/author/icondirectories.t
=> FAIL: Tests fail:
   Failed test 'opac_icon_directory: koha-tmpl/opac-tmpl/xslt/itemtypeimg exists'
- Apply the patch
- Run
  $ prove xt/author/icondirectories.t
=> SUCCESS: Tests pass and don't raise warnings.
- Sign off

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>