you can not used a service template (foo@.service) without parameter
in a specfile with the %service_add/del macros:

%preun cts
%service_del_preun pacemaker-cts-dummyd@.service

%postun cts
%service_del_postun pacemaker-cts-dummyd@.service


this will just result in errors during uninstall
of the package:
(1/1) Removing pacemaker-cts-1.1.18+20180430.b12c320f5-1.4.noarch
........[done]
Additional rpm output:
Failed to stop pacemaker-cts-dummyd@.service: Unit name
pacemaker-cts-dummyd@.service is missing the instance name.
See system logs and 'systemctl status pacemaker-cts-dummyd@.service' for
details.
Failed to get load state of pacemaker-cts-dummyd@.service: Unit name
pacemaker-cts-dummyd@.service is neither a valid invocation ID nor unit name.