Adds unit test cases to impl_qpid

Change-Id: I0c056efd9fb8b48d02a11dfb969ee98b736ba017
Closes-Bug: #1255239
Expose PublishErrorsHandler through oslo.messaging

Fix up the imports so that the log handler for publishing
error messages is available through the oslo.messaging
package instead of users having to know the full path
inside the sub-module.

Change-Id: I5c8ddaf451f7c977d8c400fe920512cdafbc7fdf
Merge "Expose PublishErrorsHandler through oslo.messaging"
Merge "Adds unit test cases to impl_qpid"