Add some basic test cases ensuring dns__zone_updatesigs() behaves as expected. (cherry picked from commit8b9d2c27b4) (cherry picked from commit3e93e4bb62) (cherry picked from commit505267f320)
Add some basic test cases ensuring dns__zone_updatesigs() behaves as expected. (cherry picked from commit8b9d2c27b4) (cherry picked from commit3e93e4bb62) (cherry picked from commit505267f320)