* pass through nxdomain results
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* return srvfail and nodata results
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* add test
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* cover more response cases
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>