Checking FailedMessage header as well for determining the ProcessingEndpoint. Fixes https://github.com/Particular/ServiceControl/issues/405
ReceivingEndpoint value is now correct for failed msgs

When messages are sent from SendOnly endpoints and endup in the error queue, the value assigned to the ReceivingEndpoint was incorrect. Added acceptance tests to cover this. Fixes https://github.com/Particular/ServiceControl/issues/405
Merge pull request #412 from Particular/issue-405

Processing error messages properly when originating from SendOnly endpoints