upstream commit: 356d1833b638bd465672aefeb71def3ab93fc17d
Note that when a new netns is created, it inherits its
sysctl_tcp_rmem and sysctl_tcp_wmem from initial netns.
This change is needed so that we can refine TCP rcvbuf autotuning,
to take RTT into consideration.
Signed-off-by: Hongbo Li <herberthbli@tencent.com>