need to set 'api_workers = 10' in /etc/neutron/neutron.conf, it works on my environment (when I found the same problem in https://bugs.launchpad.net/neutron/+bug/1321626).
need to set 'api_workers = 10' in /etc/neutron/ neutron. conf, it works on my environment (when I found the same problem in https:/ /bugs.launchpad .net/neutron/ +bug/1321626).