sampling: remove ethtool dependency

The flags are already part of the link object. There was no good
reason to ask the system again for this data.

Change-Id: I9ae5b5a017c954d0c3c2c0b6f3f62c08ee05bd4f
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/32360
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>