[kio_search] Fix warning, add UDSEntry for "." in listDir

Summary:
Every KIO listDir implementation requires a UDS entry for ".",
see D20100.

Reviewers: Baloo, Frameworks, ngraham, astippich, poboiko

Reviewed By: Baloo, ngraham

Subscribers: kde-frameworks-devel

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D20456