[krunner] Don't set the position three times in a row

Summary:
loadConfig calls setFreeFloating. setFreeFloating calls
setLocation

Reviewers: Plasma, apol

Reviewed By: apol

Subscribers: pereira.alex, ngraham, broulik, plasma-devel

CCBUG: 416145
Tags: Plasma

Differential Revision: https://phabricator.kde.org/D28366