add support for keystone federation
add support for keystone federation

This adds the Apache mod_auth_openidc and mod_auth_mellon packages to
the Keystone container to support Keystone federation (as described in
https://docs.openstack.org/keystone/9.3.0/configure_federation.html)

Change-Id: Ia32176eb33737e6f7425bd5e63b4f95eb595cd5f

rahulunair/kolla,rahulunair/kolla,stackforge/kolla,openstack/kolla,openstack/kolla,stackforge/kolla,stackforge/kolla