Bug#881771: Unclear which interface name will be used

[Greg Wooledge <wooledg@eeg.ccf.org>]

In the release notes, there's a udevadm command which is supposed to
tell us what the new interface name will be, but I had some trouble
interpreting the output.

wooledg:~$ udevadm test-builtin net_id /sys/class/net/eno1 2>/dev/null
ID_NET_NAMING_SCHEME=v240
ID_NET_NAME_MAC=enxa08cfdc389e0
ID_OUI_FROM_DATABASE=Hewlett Packard
ID_NET_NAME_ONBOARD=eno1
ID_NET_LABEL_ONBOARD=enOnboard Lan
ID_NET_NAME_PATH=enp0s31f6

That's after the upgrade to buster; I did not save the results from
before the upgrade, but basically it would have been the same command
with /sys/class/net/eth0 as the final argument, with the same output.

I thought the new interface name would be enp0s31f6 but it turned out
to be eno1 instead.

tl;dr: there's nothing "predicatable" about these names.