#170 DNS test falsely reports GREEN

[David Dyer-Bennet]

I had some connectivity failure early this morning.
When I looked at the bigsis display, I was puzzled to
see DNS shown as green for full1.gandi.net and full2.
gandi.net (which are, I assure you *outside* my local
net!).

Thomas reports: The problem is that Big Sister uses
the "host" command in order to throw a DNS request
on the target server and it seems "host" does not set
its exit code appropriately any more.

I've got bind-utils-9.1.3-4 installed from RedHat RPM;
that's somewhat old, you might want to check if more
recent versions are better behaved before rewriting
the test from scratch or something drastic.