It is not possible to configure the Ambari Server instance (ambari.properties) via Blueprints. The idea is Ambari Server is already setup and configured, then you use Blueprints for cluster install.
You'll need to automate running "ambari-server setup-ldap" (and the other Ambari Server setup commands), or handle modifying the ambari.properties file to get the Ambari Server configured how you want. Then use the Server with a Blueprint for cluster install.
Hope this helps.