Update is_up from Service OVO class to match ORM

Our services' update_at field is also being updated now on creation [1],
so there's no longer a need to check for the created_at field for the
heartbeat in is_up method.

Since this change was introduced in Newton it is now safe for this patch
to remove the unnecessary check on created_at in method is_up of the
Service OVO class.

[1] https://review.openstack.org/#/c/318572/22/cinder/db/sqlalchemy/models.py@73

Trivialfix

Change-Id: Id0e30656901810128415fd9544c28cafb22c6592

cinder/objects/service.py

@@ -194,9 +194,8 @@ class Service(base.CinderPersistentObject, base.CinderObject,
     @property
     def is_up(self):
         """Check whether a service is up based on last heartbeat."""
-        last_heartbeat = self.updated_at or self.created_at
-        return (last_heartbeat and
-                last_heartbeat >= utils.service_expired_time(True))
+        return (self.updated_at and
+                self.updated_at >= utils.service_expired_time(True))
 
 
 @base.CinderObjectRegistry.register

cinder/tests/unit/fake_service.py

@@ -30,7 +30,7 @@ def fake_db_service(**updates):
     NOW = timeutils.utcnow().replace(microsecond=0)
     db_service = {
         'created_at': NOW,
-        'updated_at': None,
+        'updated_at': NOW,
         'deleted_at': None,
         'deleted': False,
         'id': 123,