Cloned from launchpad blueprint https://blueprints.launchpad.net/nova/+spec/logging-uses-notifications. Description: Convert all INFO and ERROR log messages to Notifications so they can be properly consumed by Ceilometer and other downstream applications. Only Debug level will remain as pure log messages. This also means we need to make the Logging Notification Driver enabled by default so we don't break backwards compatibility. Specification URL (additional information): None