Comment 4 for bug 1446575

After deep analysis it turned out that Heat does not create backup resources properly in the case below.
That happens because of following:
0. Server (..ks41) in the second template has a reference to Neutron Port.
1. When Heat is trying to update the server first time everything is working correctly.
1. When Heat is trying to update the failed server (...ks41) second time it is trying to re-create it.
2. During re-creation Heat is backing up failed server independently of stack-update result and saves that resource to DB. (but the Port was not saved because there were no updates for it)
3. When Heat is trying to delete stack we have got an error because the server has a reference to the port but the port does not exist in the template.
So I suppose we should prohibit backing up of failed resource in the case above.