netns: always provide the id to rtnl_net_fill()

netns: always provide the id to rtnl_net_fill()

The goal of this commit is to prepare the rework of the locking of nsnid
protection.
After this patch, rtnl_net_notifyid() will not call anymore __peernet2id(),
ie no idr_* operation into this function.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Orabug: 23634951
(cherry picked from commit cab3c8ec8d57ef48ed754ee7acf2b9bdce80fa5f)
Signed-off-by: Cathy Zhou <Cathy.Zhou@Oracle.COM>
Reviewed-by: Jack Vogel <jack.vogel@oracle.com>
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>