Register klipper DBus interface when in non-standalone mode

Summary:
There's no reason to have different behaviour depending on whether the
UI is presented in an applet or not.

Test Plan: Looked in qdbusviewer

Reviewers: Plasma

Subscribers: graesslin, heikobecker, broulik, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D7536