Addition of InstanceUUID to facts (#4424)

The Instance UUID(refered to as PersistenceUUID in the API) is a the ID
vcenter uses to idenify VMs.
My use case for this is that I configure Zabbix using ansible and its
vmware module relies on using these to identify VMs.

lib/ansible/modules/cloud/vmware/vsphere_guest.py

@@ -1556,6 +1556,7 @@ def gather_facts(vm):
         'hw_guest_full_name':  vm.properties.config.guestFullName,
         'hw_guest_id': vm.properties.config.guestId,
         'hw_product_uuid': vm.properties.config.uuid,
+        'hw_instance_uuid': vm.properties.config.instanceUuid,
         'hw_processor_count': vm.properties.config.hardware.numCPU,
         'hw_memtotal_mb': vm.properties.config.hardware.memoryMB,
         'hw_interfaces':[],