Fixed vm tags.

Some tags were returning None because of bad decorator.

ccnode/hypervisor/domains/vm_tags.py

@@ -22,7 +22,7 @@ def _vir_tag(func):
         if not dom.hypervisor.handler.virt_connected:
             return
         try:
-            func(dom)
+            return func(dom)
         except libvirt.libvirtError:
             logger.exception('Unexpected libvirt error')
             dom.hypervisor.handler.virt_connect_restart()