[c-nsp] IP Accounting for IPv6

[Chris Mason]

> For anyone elses benefit, this seems to work (15.0(1)M6):
>
> flow record IPv6-FLOW-RECORD
>  match ipv6 destination address
>  collect ipv6 source address

Typo, the above should be "match" for the source as well to create an
aggregate based on src/dst.

Chris