The attribute_list is sorted with qsort; but indeed the first
entry of attribute_list should point to "data" even after the qsort,
because the first record has id SDP_ATTR_RECORD_HANDLE, whose
numeric value is zero.
but no one ever writes attribute_id. So it only works if qsort is
stable, and who knows what else is broken, but we can fix it by
setting attribute_id in the while loop.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>