GATEWAY-3383: Fixed auditing for DS and DS Deferred.

1. Added nhin target to audit
2. Due to the fact that DS and DS Deferred Request and Responses re-uses the same messages but will have different audit entries (ex. RegistryResponse is a response for DS sync but a request for DS Deferred Response), a flag was added to determine whether the message is being processed in the requesting gateway or responding.
3. Fixed missing audits.