Bug fix for calculating required light frames

Summary: Determining whether a job needs to capture frames was wrong for the situation that "Remember job progress" was selected and "Repeat until terminated" was selected as completion condition. In this case the scheduler assumed that no frames need to be captures when there were already some frames existing. This is wrong, the scheduler should start capturing no matter how many frames already exist.

Test Plan: Check all completion conditions both for "Remember job progress" is on and off.

Reviewers: mutlaqja, TallFurryMan

Reviewed By: mutlaqja

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D20682