Comment 4 for bug 1418911

Investigations on the lab (6.0 release, with oslo_messaging heartbeats disabled for neutron) showed that the root cause is keystone timeouting authorization requests for neutron when nova tries to fetch port that was just created - so nova thinks network creation failed on a compute and reschedules instance to another compute which creates new port in neutron for the same instance.
So we think that this might a manifestation of https://bugs.launchpad.net/mos/+bug/1413341
However this should be proven on a lab with repro.

Meanwhile the bug was filed for nova: https://bugs.launchpad.net/nova/+bug/1423845
I'm going to backport fix once it merged in upstream.
This one should also be verified on the lab with repro.