dhcp: gracefully handle overlong host name values

[Dusty Mabe <dusty dustymabe com>]

Hi all,

I'd like to highlight a bug that was opened recently and see if we can start
some discussion on it in the ticket:

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/572

It's become a bit of a sticking point when trying to figure out the proper fix
for an issue we're having in the openshift OKD / Fedora CoreOS community. See
https://github.com/coreos/fedora-coreos-tracker/issues/649

We brought the issue to NM in an attempt to fix it at an appropriate point in
the stack, rather than propagating hacks in different places.

Thanks for any discussion/consideration you put forward on this topic.

Dusty