Comment 3 for bug 1438040

copy pasting the IRC discussion with hanzhang who is able to reproduce this bug while migrating a large VM :

<hanzhang> when nova live-migrate a VM, it will first create VIF in destination node but not update port host info, then the ovs agent in destination scans this VIF and update the Port status BUILD
<hanzhang> when migrate finish, nova update the port host info with destination node, but now the Port status is BUILD

this is a corner case of the BUG 1274160