backport: stein
If I deploy monasca by setting enable_monasca to true, the monasca_notification
restarts with the following error:
ERROR:__main__:MissingRequiredSource: /var/lib/kolla/config_files/notification_templates/* file is not found
These templates are optional, so we need to mark this directory as optional in
config.json.
Change-Id: Ia2dd835daa7ab1153617cc92f17c2d8d498c73e0
Closes-Bug: #1823726
a0e214115c