Because some of the CI tests fail randomly while grepping for the
test success marker, let's be specific of the file format grep will
search to eleminate all failure sources.
This finally allows running the test suite completely in a rootless container:
```
❯ podman run \
--user 0 \
-v /dev:/dev \
-v ./:/dracut \
-it \
quay.io/haraldh/dracut-fedora:33 \
bash -c 'cd /dracut; make DRACUT_NO_XATTR=1 check'
```
Harald Hoyer