the bug exists in little-endian machine, it was not triggered due
to the difference of memory ordering between little/big endian
machines. Instead of relying on possibly modified value during
function invokcations, use saved copy of ifr.ifr_addr.sa_family.
Also add a comment at the top of ifconfig.c clarifying the issue
so the bug won't re-appear.
Approved by: jake
Reviewed by: yar