Slow down the busy indicator's rotation speed
Summary: The busy indicator spins really fast and it's kind of disorienting. Let's slow it down.
Please excuse the slight choppiness of the video; it's not like that in real life.
Reviewers: VDG, filipf, cullmann
Reviewed By: VDG, filipf, cullmann
Subscribers: filipf, plasma-devel, cullmann
Differential Revision: https://phabricator.kde.org/D22630