Correct issue with filter-autofocus and meridian flip

Summary:
When autofocus on filter change, and a sequence starts right after a meridian flip,
the align and autofocus were both activated, and then competed for the same camera.
This fixes that issue.

Test Plan:
try to get a meridian flip running right after a sequence is completed and another starts with a different filter.
Make sure auto-focus-with-filter-change is set.
This should wait on the autofocus until the meridian flip's alignment is done.
Previously the autofocus started up together with the alignment.

Reviewers: mutlaqja

Reviewed By: mutlaqja

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D27274