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'
```
New systemd defaults to generating MAC addresses for software devices (whereas
previously they would inherit them from the first enslaved slave).
Sadly, among the things this breaks is our test fixture, where the dhcp servers
are configured to expect a particular MAC address. Disable this for the
affected tests, which are essentially the ones that use bridges and bonds.
If the network-manager plugin is used instead, it wouldn't write out
ifcfg files and we wouldn't have anything to check.
While at that, also enable the test.
The IFCFG test will make sure the network-legacy plugin keeps writing
out correct ifcfg files.
This is a separate commit so that actual changes are visible in the
following one.
Harald Hoyer