Server Roles: provide an API for setting CA renewal master
    
    `ipa config-mod` gained '--ca-renewal-master' options which can be used to
    set CA renewal master to a different server. Obviously, this server has to
    have CA role enabled.
    
    https://fedorahosted.org/freeipa/ticket/5689
    http://www.freeipa.org/page/V4/Server_Roles
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Pavel Vomacka <pvomacka@redhat.com>