Add cell field to Destination object

This will allow us to request the scheduler limit a scheduling decision to a
specific cell.

Change-Id: I020900ff682f54fafe3e94789c5731ef4748679b

nova/objects/request_spec.py

@@ -612,7 +612,8 @@ def migrate_instances_add_request_spec(context, max_count):
 @base.NovaObjectRegistry.register
 class Destination(base.NovaObject):
     # Version 1.0: Initial version
-    VERSION = '1.0'
+    # Version 1.1: Add cell field
+    VERSION = '1.1'
 
     fields = {
         'host': fields.StringField(),
@@ -620,8 +621,16 @@ class Destination(base.NovaObject):
         # and also remove the possibility to have multiple nodes per service,
         # let's provide a possible nullable node here.
         'node': fields.StringField(nullable=True),
+        'cell': fields.ObjectField('CellMapping', nullable=True),
     }
 
+    def obj_make_compatible(self, primitive, target_version):
+        super(Destination, self).obj_make_compatible(primitive, target_version)
+        target_version = versionutils.convert_version_to_tuple(target_version)
+        if target_version < (1, 1):
+            if 'cell' in primitive:
+                del primitive['cell']
+
 
 @base.NovaObjectRegistry.register
 class SchedulerRetries(base.NovaObject):

nova/tests/unit/objects/test_objects.py

@@ -1076,7 +1076,7 @@ object_data = {
     'ComputeNodeList': '1.16-40258d802a6ed045690a127a2088544b',
     'DNSDomain': '1.0-7b0b2dab778454b6a7b6c66afe163a1a',
     'DNSDomainList': '1.0-4ee0d9efdfd681fed822da88376e04d2',
-    'Destination': '1.0-4c59dd1288b2e7adbda6051a2de59183',
+    'Destination': '1.1-fff0853f3acec6b04ddc03158ded11ba',
     'DeviceBus': '1.0-77509ea1ea0dd750d5864b9bd87d3f9d',
     'DeviceMetadata': '1.0-04eb8fd218a49cbc3b1e54b774d179f7',
     'DiskMetadata': '1.0-e7a0f1ccccf10d26a76b28e7492f3788',