CSIT Sporadic failures - vpnservice suite - VMs in one network do not receive ip addresses

example:

https://logs.opendaylight.org/releng/jenkins092/netvirt-csit-1node-openstack-ocata-upstream-stateful-carbon/31/log.html.gz#s1-s4-t5-k22

this is happening every time in every Ocata job.

it is the exact same suite that is passing in the Newton job.

in the Ocata job, there are two networks created each with a single subnet.
only the VMs on the first subnet are not receiving their IPs. The VMs in
the second subnet are ok.

an email thread with some discussion is here:
https://lists.opendaylight.org/pipermail/netvirt-dev/2017-June/004688.html