Pass va_list as such, instead of passing to variadic function

Summary: Logs from krdc appear corrupted for me. This patch should fix values in the logs.

Reviewers: kossebau, uwolfer, #kde_applications, cfeck, aacid

Reviewed By: #kde_applications, aacid

Subscribers: aacid

Differential Revision: https://phabricator.kde.org/D20118