Keystone federation down not install a default sso_callback_template.html

[PerToft]

When Keystone federation is enabled for e.g. SAML2, a redirect html page is required in /etc/keystone/sso_callback_template.html.

Its possible to customize this redirect file using the variable defined in defaults.yml
# NOTE(cloudnull): Tunable SSO callback file file-based overrides If defined,
# it'll be read from the deployment host, interpreted by the
# template engine and copied to the target host.
# keystone_sso_callback_file_path: "/etc/openstack_deploy/keystone/sso_callback_template.html"

But when the keystone_sso_callback_file_path is not defined and keystone_sp != {} a default template should be installed.