Untie subobject versions

Since obj_relationships was removed in
Iea8b6348e3b01aaa335ec5408f07826f1e758d20 because manifest backports are
now used, most parent object versions will no longer change when a child
object is changed. Because of this, some objects that have a child
version tied to a parent version no longer need to be tied. The versions
can progress individually on their own. The child is all grown up now,
he's moving out of his parents' basement, buying a car, and going on to
make his parents proud.

Change-Id: Ie0c7bd419e3490d01f73c7a39cd2666eafcf9539

nova/objects/image_meta.py

@@ -133,7 +133,7 @@ class ImageMetaProps(base.NovaObject):
     # Version 1.5: added os_admin_user field
     # Version 1.6: Added 'lxc' and 'uml' enum types to DiskBusField
     # Version 1.7: added img_config_drive field
-    VERSION = ImageMeta.VERSION
+    VERSION = '1.7'
 
     # Maximum number of NUMA nodes permitted for the guest topology
     NUMA_NODES_MAX = 128

nova/objects/vcpu_model.py

@@ -55,7 +55,7 @@ class VirtCPUModel(base.NovaObject):
 
 @base.NovaObjectRegistry.register
 class VirtCPUFeature(base.NovaObject):
-    VERSION = VirtCPUModel.VERSION
+    VERSION = '1.0'
 
     fields = {
         'policy': fields.CPUFeaturePolicyField(nullable=True),