You get a
not valid ifname error if you try to run tests with underscores in them or if the interface name is too long. There's two things we can do for that:
Shorten the absurdly long interface name that is prepended to the mark.
Here it is in action: https://jenkins.aws.isc.org/job/kea-manual/job/tarball-system-tests/90/
And here it is failing, before the changes: https://jenkins.aws.isc.org/job/kea-manual/job/tarball-system-tests/85/