Save unneeded DBus roundtrip

Summary: When the module is loaded the handler is notified over DBus just to go back to the module to init it. Skip the roundtrip and init directly.

Test Plan: Restarted plasmashell and kded5. (dis)connected wifi. Got notifications about it

Reviewers: #plasma, jgrulich

Reviewed By: jgrulich

Subscribers: davidedmundson, broulik, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D28698