Don't create thumbnails for encrypted Vaults
Summary:
This patch makes PreviewJob skip thumbnail generation on fuse.encfs and fuse.cryfs mounts.
BUG:404750
Reviewers: davidedmundson, dfaure
Reviewed By: davidedmundson
Subscribers: broulik, kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D19979