update kcm statistics in kcmshell too

Summary:
also when opening modules with kcmshell (used a lot with krunner)
the statistics need to be updated to keep the list on systemsettings startup
up to date and have complete usage data of kcm modules

Test Plan:
opened systemsettings and a module with kcmsell, the list gets updated
on the fly

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: davidedmundson, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D6112