Comment 9 for bug 1830763

According to issue with reaching metadata service from vm and ssh failure. I think I found what is the reason.
It is race condition when 2 routers are created in short time and configured on same snat node. Then when both routers are configuring external gateway it may happend that one of routers will add external net to subscribers list in https://github.com/openstack/neutron/blob/master/neutron/agent/l3/dvr_fip_ns.py#L129 so second router will got info that it's not "first" and will go to update gateway port instead of creating it.
But if in fact gateway wasn't created yet it will cause exception in: https://github.com/openstack/neutron/blob/master/neutron/agent/l3/dvr_fip_ns.py#L332
And if this will happend, one of routers will not have properly configured iptables rules to allow requests to 169.254.169.254 so metadata will not work for this instance.