CreateJob: connect to progress() signal instead of KJob::percent()

Summary:
Another attempt at fixing #402824 after ce2f7f6690be.

This should fix progress reporting also for libzip and libarchive plugins.
The problem with those plugin is that CreateJob starts two nested threads.

BUG: 402824
FIXED-IN: 19.04.3

Reviewers: rthomsen

Subscribers: kde-utils-devel, Ark

Tags: Ark

Differential Revision: https://phabricator.kde.org/D21686