[NETNS][IPV4] tcp - make proc handle the network namespaces

This patch, like udp proc, makes the proc functions to take care of
which namespace the socket belongs.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

diff --cc net/ipv4/tcp_ipv4.c
Simple merge