engine: don't read external files in unit test

- Removed trying to read external files that should be there but
  in certain situations are not there. Modified it to just read files
  inside the source tree.

Change-Id: I47db3324daf11a19cb76c3866a3f4e4152b9a3a1
Signed-off-by: Alexander Wels <awels@redhat.com>