celery: add 2 statsd probes for the runner and listener
- runner: counting the number of scheduled tasks,
- listener: counting the number of processed events.
Related to #2133 (closed)
Migrated from D2394 (view on Phabricator)
Staging instance, all changes can be removed at any time
Related to #2133 (closed)
Migrated from D2394 (view on Phabricator)