For redundancy and security against catastrophic failure of a CA master, there must be more than one CA master in a topology. Replica installation is a good time to warn about this situation. Print a warning at the end of ipa-replica-install, if there is only one CA replica in the topology. Fixes: https://pagure.io/freeipa/issue/7459 Reviewed-By: Christian Heimes <cheimes@redhat.com>