DNS: dns-update-system-record can create nsupdate file
    
    Added option --out <path> creates a file with IPA DNS data in nsupdate
    format.
    
    https://fedorahosted.org/freeipa/ticket/6585
    
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>