Fix bug re filter-change-autofocus

Summary:
Added a test in Capture::captureImage() that checks to see if the filterManager is busy,
and if so, waits until it isn't. This resolves and issue where the focus and capture modules
could both be trying to take pictures, if auto-focus-on-filter-change is set, and if a filter
is changed mid-sequence, e.g. by a meridian flip causing align to run, which may run with a different filter.

Disabled auto-focus-on-filter-change for alignment. This wasn't 100% necessary to fix the above bug,
but I believe it is the right thing to do. Without this, align is likely to initiate an autofocus,
when the auto-focus-on-filter-change option is set, and then, after control passes back to capture,
another auto-focus would likely be run. Seems over the top.

Reviewers: mutlaqja, wreissenberger, lancaster

Reviewed By: mutlaqja

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D25497