Magnum was unable to fire up k8s cluster because heat-container-agent
inside kube-master was pointing to internal keystone endpoint instead of
public endpoint. This fix tells kolla ansible to set clients_keystone
auth_uri to public endpoint so that heat-container-agent communication
with heat is successfully authenticated by keystone.
Change-Id: Ida49528f88685710b5e6b8f3c4d4622506af5ae1
Closes-Bug: #1762754