ioops: misc: add dup{,2}_or_die to ioops

Bail out if it should ever fail. Detected by coverty in the
translate_pcap_to_txf() path.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
ioops: mark failure path as unlikely

Just tell GCC that those paths are unexpected.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>