nsd prolbem when being primary parent and secondary child

[Paul Wouters]

We just encountered an error between bind 9.3.x (and bind 9.4.x) and
nsd-2.3.6.

ns0.xelerance.nl is primary for xelerance.com
ns0.xelerance.nl is secondary for ssw.xelerance.com
lox.sandelman.ottawa.on.ca. is priary for ssw.xelerance.com
ns0 is configured to fetch ssw.xelerance.com from lox.

When nsd trties to fetch the ssw.xelerance.com zone, nsd-xfer gives an

	error: answer section is empty.

Removing the NS record for ns0.xelerance.nl for the onessw.xelerance.com
at the master (lox) fixes the problem, and nsd-xfer logs:

	info: send AXFR query to 205.150.200.178 for ssw.xelerance.com.

So it looks like nsd is confused when it is both primary parent, and
secondary for the child delegated by itself as parent.

Paul