Set gain each capture
Previously the gain and other custom properties were set only at the start of the capture job sequence
and not for each capture. Thus, if the sequence were interrupted, e.g. by autofocus, and the gain
or other property changed by the autofocus, it would not be restore when capture restarted.
This fixes that issue.
Reviewed By: mutlaqja
Tags: KDE Edu
Differential Revision: https://phabricator.kde.org/D24417