It's very critical to optimize the exit path for network namespaces,
because they are destroyed under net_mutex and many namespaces can be
destroyed for one iteration.
v2: use dev_set_uevent_suppress()
Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Andrei Vagin <avagin@openvz.org> Signed-off-by: David S. Miller <davem@davemloft.net>