Add img_linked_clone to compute vmware metadefs
Add img_linked_clone to compute vmware metadefs

The nova vmware driver checks images for the 'img_linked_clone' property at
boot time, but that property is missing in OS::Compute::VMware metadefs.
This patch adds 'img_linked_clone' property. No default value is specified for
this property as the default behavior in a particular cloud depends on the
nova configuration setting for 'vmware.use_linked_clone'.

DocImpact: add to metadefs release note

Change-Id: I27cd33b9b9593de61a6558879d337685ebd6f734

openstack/glance,openstack/glance,openstack/glance