场景： 计算节点备rabbitmq和dvr。断网后，再脸上，发现创建虚拟机失败。

报错：创建network失败，虚拟机的虚拟网卡创建不出来。

临时处理方法：
原因1：rabbitmq从cluter中掉出来，需要重启容器重新注册到原先rabbitmq集群

原因2：neutron服务不可用，错误如下。重启neutron-openvswitch-agent容器。
Unable to execute ['ovs-vsctl', '--timeout=10', '--oneline', '--format=json', '--', '--id=@manager', 'create', 'Manager', 'target="ptcp:6640:192.168.102.21"', '--', 'add', 'Open_vSwitch', '.', 'manager_options', '@manager']. Exception: Exit code: 1; Stdin: ; Stdout: ; Stderr: ovs-vsctl: transaction error: {"details":"Transaction causes multiple rows in "Manager" table to have identical values ("ptcp:6640:192.168.102.21") for index on column "target". First row, with UUID 616132a8-a1c1-420a-a0c7-1ed51a41064a, was inserted by this transaction. Second row, with UUID 5b9cf063-8116-42ce-9f28-209ab3912cbe, existed in the database before this transaction and was not modified by the transaction.","error":"constraint violation"}