add tarball 19.12.1 of release service and use it by default

Summary: add 19.12.1 tarball for KDE release service and switch the default to it

Test Plan: Elisa 19.12.1 release gets built

Reviewers: Windows, vonreth, cullmann

Reviewed By: Windows, cullmann

Subscribers: cullmann

Differential Revision: https://phabricator.kde.org/D26578