There is no insecure flag for quantum at all. Even in latests sources.

root@d52-54-00-12-34-0d:~# quantum --insecure net-create fixed --shared --provider:network_type gre --provider:segmentation_id 1
Invalid command '--insecure'
root@d52-54-00-12-34-0d:~#


root@ubuntu1210:/tmp/nv# git clone https://github.com/openstack/quantum
Cloning into 'quantum'...
remote: Counting objects: 31002, done.
remote: Compressing objects: 100% (11739/11739), done.
remote: Total 31002 (delta 22465), reused 25271 (delta 17336)
Receiving objects: 100% (31002/31002), 8.36 MiB | 278 KiB/s, done.
Resolving deltas: 100% (22465/22465), done.
root@ubuntu1210:/tmp/nv/quantum# git checkout stable/grizzly
Branch stable/grizzly set up to track remote branch stable/grizzly from origin.
Switched to a new branch 'stable/grizzly'
root@ubuntu1210:/tmp/nv/quantum# grep 'insecure' -i -r ./
root@ubuntu1210:/tmp/nv/quantum#