Demodulize worker names to have valid StatsD metrics.

When having workers inside namespaces the "::" in the worker name will create
invalid metric names.

The following was found on our statsd logs:

DEBUG: Bad line:  in msg "production.worker.Cassandra::NotificationMapWorker.success:1|c|@0.1"
Merge branch 'nhocki-demodulize_worker_names'