Restarting looping schedule continues capturing

Summary:
When a schedule is started that is looping AND there are already existing images in the target directory,
the capture module refuses to continue and signals that there exist already sufficent images - which
should be never the case for looping schedules.

Test Plan:
Take any schedule where the sequence is repeated infinitely often. Start it and let it run for at least
one cycle. Then abort it and restart it. Switch to the capture tab and see, that no more images will be
taken.

Reviewers: mutlaqja, TallFurryMan

Reviewed By: mutlaqja, TallFurryMan

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D14928