Notification and CDM partial update

In this changeset, I implemented the notification handling (Rx only)
system for consuming incoming notifications, more especially the Nova
ones. The notifications handlers also contain the logic which
incrementally updates the Compute model.

Change-Id: Ia036a5a2be6caa64b7f180de38821b57c624300c
Partially-implements: blueprint cluster-model-objects-wrapper

watcher/decision_engine/messaging/audit_endpoint.py

@@ -30,6 +30,7 @@ LOG = log.getLogger(__name__)
 
 
 class AuditEndpoint(object):
+
     def __init__(self, messaging):
         self._messaging = messaging
         self._executor = futures.ThreadPoolExecutor(