ip6-nd: initialize radv_info->send_radv to 1

ip6-nd: initialize radv_info->send_radv to 1

Otherwise, the newly configured interface will never send RADV's.

See below. In the typical case, suppress = 0 and is_no = 0, which
propagates the current value of radv->send_radv:

  radv_info->send_radv =
    (suppress != 0) ? ((is_no != 0) ? 1 : 0) : radv_info->send_radv;

No other bit of code will set send_radv, at least in straightforward
ways.

Type:fix

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: If9368155f7676460ca1f87729c2b3c453405d08d