Comment 4 for bug 1714289

Having this in localrc, seems to prevent this kind of conflict:

IPV4_ADDRS_SAFE_TO_USE=10.1.0.0/20

It happens to be absent from the localrc of faulty jobs, e.g.:
- http://logs.openstack.org/87/497587/1/check/gate-group-based-policy-dsvm-aim-ubuntu-xenial-nv/76af3b2/logs/local.conf.txt.gz
- http://logs.openstack.org/29/480229/6/check/gate-networking-bagpipe-dsvm-fullstack-ubuntu-xenial-nv/163cb5b/logs/local.conf.txt.gz

Something somewhere in the labyrinth of devstack gate scrips is so that these jobs don't inherit what would help them avoid this issue such as [1] or [2].

[1] http://git.openstack.org/cgit/openstack-infra/project-config/tree/jenkins/jobs/devstack.yaml#n16
[2] http://git.openstack.org/cgit/openstack-infra/devstack-gate/tree/devstack-vm-gate.sh#n52