dns: re-introduce --raw in dnsrecord-del
    
    The flag was removed in commit ff52c25ae299abba8bed653fe324951979a41293
    because it is unused. Add it back for compatibility with old clients.
    
    https://fedorahosted.org/freeipa/ticket/5644
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>