Description
If ATS's DNS response was N A records, and one is unavailable ATS will always send traffic to the down origin regardless of configuration. This bug seems to be due to how hostdb is keeping track of DNS + health of the origin.
Regression was introduced in https://issues.apache.org/jira/browse/TS-3237 (https://git-wip-us.apache.org/repos/asf?p=trafficserver.git;h=a8d1862).