[j-nsp] Duplicate IP addresses on interfaces

[Harry Reynolds]

Well, I cannot comment farther on the merits. Proves you cannot please
all, all the time. I know folks get really mad when we break a
previously working config, which is why we (had) to allow on a ptp.

That said, I could not find any clear documentation as to how we handle
this, and was a bit surprised by the partial commit business. So, I have
raised doc-cmd/390788 to at least get the behavior documented.

Thanks