Reproducer for bug in structured dnsrecord_show
    
    "RuntimeError: dictionary changed size during iteration" in
    ipaserver/plugins/dns.py", line 3209, in postprocess_record
    
    https://pagure.io/freeipa/issue/7275
    
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>