send IOTHUB_CLIENT_CONNECTION_COMMUNICATION_ERROR of failed PUBACK DC messages

[ericwolz]

Checklist

• I have read the [contribution guidelines] (https://github.com/Azure/azure-iot-sdk-c/blob/master/.github/CONTRIBUTING.md).
• I added or modified the existing tests to cover the change (we do not allow our test coverage to go down).
• If this is a modification that impacts the behavior of a public API
  • I edited the corresponding document in the devdoc folder and added or modified requirements.
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  • This pull-request is submitted against the master branch.
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Reference/Link to the issue solved with this PR (if any)

Description of the problem

Fix for issue #1255 was partially correct. There was a missing connection status callback in the affected code, however the status to be raised should be COMMUNICATION_ERROR, not RETRY_EXPIRED. RETRY_EXPIRED must only be raised on the code path that actually deals with retry policy checks.

Description of the solution

Replace the connection status callback value of RETRY_EXPIRED by COMMUNICATION_ERROR.