Add SSL PKI properties for keystone

To implement the SSL PKI spec we need to use property names that can be
generalized to all services. Adding new properties to support this for
the keystone ssl cert and cert key, while still supporting the old
properties for backwards compatibility.

Change-Id: Id1b8d8ff6d55d74f38b19d89f76001f374c55393
Merge "Add SSL PKI properties for keystone"