convert ServiceInfoHelper to a namespace, since the only usage is to
call it's static method

Change-Id: I908bdbc06cbdb6b72ee1ae469ff207b2fca69963
Reviewed-on: https://gerrit.libreoffice.org/44533Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>