Fix long standing mediaopt setting bugs seen on sparc64. Though 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.
Fix long standing mediaopt setting bugs seen on sparc64. Though
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

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