[c-nsp] LDPv6 Census Check

[Drikus Brits]

We're deploying some new POPs with a mix of IOS-XR as borders, BNG and
PEs and IOS-XE for LNSs. LDPv6 would be awesome to have availabke on
IOS-XE alongside LDPv4. We're being pushed by Cisco to go one flavour
or another of SR as well by Cisco, but i'd much prefer to have LDPv4 &
LDPv6 right now.

We have some buying power with Cisco at the moment, so let me know how
I can help from the land 'down under'.

Drikus.