This commit adds support for the olso.messaging AMQP 1.0 driver to
support notifications.
This patch:
* use oslo::messaging::amqp resource
* add keystone::messaging::amqp class for oslo_messaging_amqp opts
* add spec tests for amqp class options
* add feature release note
Change-Id: I4b56417ce8ee7502ad32da578bdc29c46e459bd5