net: Modify sk_alloc to not reference count the netns of kernel sockets.

Now that sk_alloc knows when a kernel socket is being allocated modify
it to not reference count the network namespace of kernel sockets.

Keep track of if a socket needs reference counting by adding a flag to
struct sock called sk_net_refcnt.

Update all of the callers of sock_create_kern to stop using
sk_change_net and sk_release_kernel as those hacks are no longer
needed, to avoid reference counting a kernel socket.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/net/inet_common.h
Simple merge

diff --cc include/net/sock.h
Simple merge

diff --cc net/core/sock.c
Simple merge

diff --cc net/ipv4/af_inet.c
Simple merge

diff --cc net/ipv4/udp_tunnel.c
Simple merge

diff --cc net/ipv6/ip6_udp_tunnel.c
Simple merge

diff --cc net/l2tp/l2tp_core.c
Simple merge

diff --cc net/netfilter/ipvs/ip_vs_sync.c
Simple merge