In the process of handling instance_created.end,
there is a KeyError exception output log. This is because
invoking get_instance_by_uuid before creating the instance
in the data model.
During the review of https://review.opendev.org/#/c/663489/,
reviewers think that it's better to remove the KeyError exception.
This patche seperates the process of instance_created.end from
other Nova notifications and removes the call of get_instance_by_uuid.
Change-Id: Ie9e2d4f5b32ee7a5b52bbcd50abfa81dcabab7bb
dd321e9f21