nslookup incorrect exit code

[Slava Bacherikov]

Hi,

It looks like busybox recently changed behavior of nslookup and this
broke some scripts. Previously, nslookup returned 1 as exit code if DNS
server returned NXDOMAIN, or some other failure. Actually, nslookup from
bind-utils also have same behavior.

But recently, nslookup in busybox return zero exit code in case of
NXDOMAIN or some other failure.

Few examples:

original nslookup:
nslookup baddomain > /dev/null; echo $?
1

busybox:
nslookup baddomain > /dev/null; echo $?
0

original nslookup:
nslookup busybox.net 205.251.193.145 > /dev/null; echo $?
1

busybox:
nslookup busybox.net 205.251.193.145 > /dev/null; echo $?
0

Here's one of use cases where it was used:
https://kubernetes.io/docs/concepts/workloads/pods/init-containers/#init-containers-in-use
. Now this is broken.

I've also attached patch that mimic old behavior.
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