ssl: Add support for a CA Certificate

Add SSLCACertificate to the overcloud yaml.

This allows a CA certificate to be specified in cases where the Cert
does not come from a CA in the system bundle.

Partially implements: blueprint tripleo-ssl-overcloud

Full set of blueprint changes:

https://review.openstack.org/#/c/85098
https://review.openstack.org/#/c/85099
https://review.openstack.org/#/c/85100

Change-Id: I67d7c1362df323762023be5c74fbe75b1583570c
Merge "ssl: Add support for a CA Certificate"