check if IFA_F_NODAD if defined

Original patch included ifdef:
https://github.com/tuxis-ie/keepalived/commit/b0d25a0bc5662caa4931f79b5731928e186bbdaf

Will fix the issue for:
http://sourceforge.net/mailarchive/forum.php?thread_name=CAECz2C3bFyaiXwCb4t1-nJCmhXu64tDEejCxQuvf%3DrbUjDE5KA%40mail.gmail.com&forum_name=keepalived-announce