Comment 7 for bug 1562878

I've had a look at the logs that match the criteria Henry set in comment #5, and I believe these are 2 different problems:

* the original problem reported by Ann concerns HA routers and specifically (afaiu) the HA subnet to which interfaces are being added by one process while another process tries to delete it since it thinks it's no longer needed. In this case, a solution such as ALLOCATING for networks is suitable (though a way overkill - we might as well make this a silent error and just catch the exception).

* the criteria Henry set looks like the subnet has nothing to do with HA (the router in question isn't an HA router at all). I've looked at [1], and specifically the screen-q-svc.txt.gz, looking for the subnet that failed in that run [2] (bb64edc3-2b1e-45ef-a199-5395918c72d7).

As such, I think it's best to treat them as 2 different issues, and since it's a critical error and I'm not so sharp on DVR it's best if someone else take it instead.

[1]: http://logs.openstack.org/86/335786/20/gate/gate-tempest-dsvm-neutron-dvr/36c90cd/logs/console-q-svc.txt.gz
[2]: http://logs.openstack.org/86/335786/20/gate/gate-tempest-dsvm-neutron-dvr/36c90cd/console.html