debian-stretch-titan: Wait for interface to be _up_ not just its existance
I've seen at least one instance where -EIFDOWN was returned when the test suite was coming up. This is a race condition, as we first have to move the netdev into the namespace and only then can configure it. "pipework wait" only waits for its existence, not until it is up.
We cannot revert the order, as the netdev looses its state when it is moved to a different netns.
