Use consistent default Kickoff user icon
Summary:
Add the 22px default user icon that is used everywhere else.
Test Plan: Open Kickoff.
Reviewers: Plasma, VDG, ngraham
Reviewed By: VDG, ngraham
Subscribers: ngraham, VDG, kde-frameworks-devel, Plasma
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D20536