Fix bad libvirt behaviour.

Sometimes, libvirt tells us too late that a domain has been removed.

cloudcontrol/node/hypervisor/domains/vm_tags.py

@@ -23,7 +23,13 @@ def _vir_tag(func):
             return
         try:
             return func(dom)
-        except libvirt.libvirtError:
+        except libvirt.libvirtError as exc:
+            if 'Domain not found' in str(exc):
+                # sometimes, libvirt tells us too late when a domain is removed
+                # we just ignore the error and remove the domain
+                dom.hypervisor.domains.pop(dom.name)
+                dom.tag_db.remove_sub_object(dom.name)
+                return
             logger.exception('Unexpected libvirt error')
             dom.hypervisor.handler.virt_connect_restart()