Comment 4 for bug 1609526

We have run into this issue on Mitaka as well. Its not happening for the same reason i.e glance image failing to download.

For us, one of the hypervisors did not have propert virt enabled which caused the instance launch to fail on that hypervisor and reschedule on a different one. However, the port that was created while the instance was attempting to launch on the first one was still there and not cleaned up.

Result was two ports attached to the instance and only one of them being in use.