docker: wire SELinuxMode with Ansible vars
docker: wire SELinuxMode with Ansible vars

When SELinuxMode is set to enforced in thedeployment, configure Docker
to enable SElinux.

It'll wire container_registry_selinux variable in ansible-role-container-registry
which enables --selinux-enabled if set to True.

Change-Id: Ic030ecbe8b6719ba45cb7c27c6cf44bab14fed88

openstack/tripleo-heat-templates,dprince/tripleo-heat-templates,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates