create a separate test file for embedded images test

Summary:
if the test.jpg file is altered, e.g. additional
metadata is added, the embedded images test fails.
create a separate cover test file from the existing one
for this test.

Reviewers: bruns

Reviewed By: bruns

Subscribers: kde-frameworks-devel, Baloo

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D16560