Remove security role from user_variables.yml
Remove security role from user_variables.yml

This patch removes a confusing section of `user_variables.yml` that
is no longer needed since the security role is applied by default.

Closes-bug: 1664824
Change-Id: Iebf59288a8abbf72a961832fed113bbd30cbe77c

bunchc/openstack-ansible,BjoernT/os-ansible-deployment,BjoernT/openstack-ansible,cfarquhar/openstack-ansible,stackforge/os-ansible-deployment,BjoernT/os-ansible-deployment,cloudnull/os-ansible-deployment,cloudnull/os-ansible-deployment,bunchc/openstack-ansible,robb-romans/openstack-ansible,BjoernT/os-ansible-deployment,yanyao/openstack-ansible,yanyao/openstack-ansible,openstack/openstack-ansible,cfarquhar/openstack-ansible,BjoernT/openstack-ansible,openstack/openstack-ansible,os-cloud/os-ansible-deployment,robb-romans/openstack-ansible,os-cloud/os-ansible-deployment,stackforge/os-ansible-deployment