neutron dhcp availability bug fixes

bug description

 

When the three network control node has a node database three broken or cause hang abnormality occurs in the port neutron dhcp namespace in dhcp agent HA mode unreachable, HA manner, will generate a new device generates a new tap IP, resulting in each dhcp namespace appears in two tap devices. So dhcp unavailable. \

 

Part of the phenomenon described

https://blog.csdn.net/bc_vnetwork/article/details/52457922

 

bug fixes

 

 

Community repair

https://review.opendev.org/#/c/245413/

Code changes

https://review.opendev.org/#/c/245413/2/neutron/agent/linux/dhcp.py