Change sensu_remote_plugins default to empty list

defaults/main.yml

@@ -76,7 +76,7 @@ sensu_include_dashboard: false
 sensu_master: false
 sensu_client: true
 sensu_user_name: sensu
-sensu_remote_plugins: ~
+sensu_remote_plugins: []
 sensu_transport: rabbitmq
 sensu_client_name: "{{ ansible_hostname }}"
 sensu_client_subscriptions: "{{ group_names }}"