netns: notify new nsid outside __peernet2id()

netns: notify new nsid outside __peernet2id()

There is no functional change with this patch. It will ease the refactoring
of the locking system that protects nsids and the support of the netlink
socket option NETLINK_LISTEN_ALL_NSID.

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 3138dbf881274cb20d9aa1b307861f689e820fbe)
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>