Move remaining salt file operations into unprivileged processes

Summary:
Otherwise the salt is always recreated on with ~ on NFS with root_squash
as root does not have access.

Test Plan: Reporter confirmed that it works and fixes the issue for him.

Reviewers: Plasma, aacid

Reviewed By: aacid

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D13776