This adds the standard 'object.(create|update|delete).(start|end)'
notifications to the Pecan notification hook and adds unit tests
to exercise them.
This patch also corrects the on_error handler for untranslated
exceptions which was incorrectly raising the exception rather than
returning it. This was resulting in the other hooks not getting
the correct status code on an untranslated exception.
Closes-Bug: #1552979
Change-Id: I400f8d3988db204caed25e7c848a415b45d47172
e433c2870a