[neutron] Patch fails to build after rechecking.

Hello guys, I've been working on a patch of neutron https://review.openstack.org/#/c/626109/11 and it keeps failing when building. I'm sure my code is bug free and I found Liu Yulong's patch has a similar condition like mine. https://review.openstack.org/#/c/627285/. He rechecks many times and fails every time. His code is nearly the same as previous except a line of comment. I'm not sure if there's any bug on this checking system and please take a look at our issue, thank you.