Comment 4 for bug 1790569

@Matt Riedemann, I am so sorry to say that, the LOG in #1 is not exact.

I meet this problem only once, step like this:
1. Gigrate an Instance VM-1 from node-0 to node-1.
2. Scheduler recieved the message and claim resouces for VM-1 on node-1.
3. However, if RabbitMQ exception for pressure overload or other resaon, conductor can not received a response , and migration becomes error.
4. At last, the resources allocated for VM-1 on node-1 leaved that, can not be cleaned.