Bug fix in Scheduler for pausing after capturing sequence

Summary:
Pressing the "Pause" button of the Scheduler module did not work properly when a capturing session was running. The scheduler paused the scheduler job after the capture sequence was completed, but pressing "Start" afterwards did not continue the execution.
In addition, the "Pause" button turns checked as soon as the scheduler pauses.

Test Plan: Start a Scheduler Job and press the "Pause" button at any stage of the scheduler.

Reviewers: mutlaqja, TallFurryMan

Reviewed By: mutlaqja, TallFurryMan

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D21531