If the user defines a list of certificates they require with the
variable prefix user_pki_certificates_, this playbook will create
the required certificates.
The use case for this functionality is to use the openstack
private CA to generate certificates for an API or client that
is not part of OSA, but needs a certificate
Change-Id: If7f57e7eb7335d6bf19a739a25d1e06de3d0cd0d
d27d4daed6