ocg: sanitize role::ocg::production, change alerts

This refactoring uses hiera instead of complex scoping overrides, and
also raises the alarm levels for the job queue to prevent it from spamming.

Change-Id: I2ca36250220ba2c47fcb47cae3bfe933b3e3bc70
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>