D18725: properly attempt to locate the kioslave bin in $libexec AND $libexec/kf5

[Harald Sitter]

sitter added reviewers: davidedmundson, dfaure.

REPOSITORY
  R241 KIO

REVISION DETAIL
  https://phabricator.kde.org/D18725

To: sitter, davidedmundson, dfaure
Cc: kde-frameworks-devel, michaelh, ngraham, bruns