Check that a zone in the process of being signed resolves

Check that a zone in the process of being signed resolves

ans10 simulates a local anycast server which has both signed and
unsigned instances of a zone.  'A' queries get answered from the
signed instance.  Everything else gets answered from the unsigned
instance.  The resulting answer should be insecure.

(cherry picked from commit d7840f4b9323938903024f9d3094c99bc9519156)