Add CADF event configurations in Keystone when enabled

By default CADF events added even if they are disbaled in all.yml.
Boolean check is missing is added so that CADF configurations will
be added only if it is enabled.

Change-Id: I757ae176228cc4e74d06ce85b27200bdcdd5dd5c
Closes-Bug: #1607904

ansible/roles/keystone/templates/keystone.conf.j2

 [DEFAULT]
 debug = {{ keystone_logging_debug }}
-{% if enable_cadf_notifications %}
+{% if enable_cadf_notifications | bool %}
 notification_format = cadf
 transport_url = rabbit://{% for host in groups['rabbitmq'] %}{{ rabbitmq_user }}:{{ rabbitmq_password }}@{% if orchestration_engine == 'KUBERNETES' %}rabbitmq{% else %}{{ hostvars[host]['ansible_' + hostvars[host]['api_interface']]['ipv4']['address'] }}{% endif %}:{{ rabbitmq_port }}{% if not loop.last %},{% endif %}{% endfor %}
 {% endif %}
@@ -44,7 +44,7 @@ memcache_servers = {{ memcached_servers }}
 memcache_servers = {% for host in groups['memcached'] %}{{ hostvars[host]['ansible_' + hostvars[host]['api_interface']]['ipv4']['address'] }}:{{ memcached_port }}{% if not loop.last %},{% endif %}{% endfor %}
 {%- endif %}
 
-{% if enable_cadf_notifications %}
+{% if enable_cadf_notifications | bool %}
 [oslo_messaging_notifications]
 driver = messagingv2
 {% endif %}