Get correct CA cert nickname in CA-less
    
    During CA-less installation, we initialize the HTTPD alias
    database from a pkcs12 file. This means there's going to
    be different nicknames to the added certificates. Store
    the CA certificate nickname in HTTPInstance__setup_ssl()
    to be able to correctly export it later.
    
    https://pagure.io/freeipa/issue/6806
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>