Support to deploy aodh-evaluator in active/active mode by leveraging
database non-locking mechanism. With this feature, there could be
multiple aodh-evaluator processes running without dependency of etcd or
zookeeper.
The main change is in aodh/evaluator/__init__.py, in order to use
non-locking db update, a new column named 'evaluate_timestamp' is
introduced to 'alarm' table. all other code is changed
because of 'storage_conn.get_alarms()' implementation changed.
Change-Id: I666817cdcf9083f2ad5871d157900cb6dc5a86e0
1349706e2e