Disable dig IDN output into scripts
    
    Dig could be used to receive zone via AXFR. If IDN data are inside and
    are decoded, it cannot be used as named zone file. Disable +idnout if
    stdin is not a tty.
    
    (cherry picked from commit 7a958a2a9f9461e4d789cf15fd0bfac005a8e491)