DNSSEC: Accept ipa-ods-exporter commands from command line.
    
    Previously only systemd socket activation was supported.
    Ability to call the command directly is handy in special cases,
    e.g. for debugging or moving key master role from one server to another.
    
    https://fedorahosted.org/freeipa/ticket/4657
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>