[nwam-dev] code review for 10682 (duplicate address)

[Anurag S. Maskey]

code review for 10682 Need a policy / process for handling duplicated 
(already used) addresses
        http://defect.opensolaris.org/bz/show_bug.cgi?id=10682

webrev is at
        http://zhadum.east/export/ws/am223141/temp/nwam1-work/webrev/

Adds "duplicate address detected" auxiliary state.  Checks the interface 
flags when handling IF_STATE event and moves to maintenance if 
IFF_DUPLICATE is seen.

Thanks,
Anurag