Destroy rescue instance if main instance is destroyed

Fixes bug 955166

If the main instance was destroyed while an instance was in rescue mode
the rescue instance would not be destroyed. Ensure it gets destroyed
too.

Change-Id: I7d411a2b532fae7ba90c0639527805f47913fce6

nova/virt/xenapi/vmops.py

@@ -1182,6 +1182,12 @@ def destroy(self, instance, network_info):
         """
         instance_uuid = instance['uuid']
         LOG.info(_("Destroying VM for Instance %(instance_uuid)s") % locals())
+
+        rescue_vm_ref = VMHelper.lookup(self._session,
+                                        "%s-rescue" % instance.name)
+        if rescue_vm_ref:
+            self._destroy_rescue_instance(rescue_vm_ref)
+
         vm_ref = VMHelper.lookup(self._session, instance.name)
         return self._destroy(instance, vm_ref, network_info, shutdown=True)