This boolean configuration option will preserve the default
keystone notification filtering when True, filtering out
successful authentication notifications, and allow all
notifications through when False. This can be useful when
capturing cadf logging events for user authentication. This
option is True by default to reduce log file bloat.
These default notifications are described in the upstream
configuration documentation under 'notification_opt_out.'
https://docs.openstack.org/keystone/latest/configuration/config-options.html
Change-Id: Ib7a90d6d5e413dfe874acdfc3ef7a43a22424afe
Signed-off-by: Myles Penner <myles.penner@canonical.com>