Delete swap VDI if not used

Fixes bug 889196

Change-Id: I08f4484310c5a35e62ca761193790a464ad15ac9

nova/virt/xenapi/vmops.py

@@ -418,10 +418,14 @@ def _attach_disks(self, instance, disk_image_type, vm_ref, first_vdi_ref,
 
         # Attach any other disks
         for vdi in vdis[1:]:
-            if generate_swap and vdi['vdi_type'] == 'swap':
-                continue
             vdi_ref = self._session.call_xenapi('VDI.get_by_uuid',
                     vdi['vdi_uuid'])
+
+            if generate_swap and vdi['vdi_type'] == 'swap':
+                # We won't be using it, so don't let it leak
+                VMHelper.destroy_vdi(self._session, vdi_ref)
+                continue
+
             VolumeHelper.create_vbd(session=self._session, vm_ref=vm_ref,
                     vdi_ref=vdi_ref, userdevice=userdevice,
                     bootable=False)