Baloo Runner: Use X-Plasma-Request-Actions-Once property in service

Summary:
Because the actions are always the same the X-Plasma-Request-Actions-Once property can be set to true.
Depends on D29175.

Test Plan: Still displays action.

Reviewers: #plasma, meven, ngraham

Reviewed By: ngraham

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D29320