Revert "ipv4/tcp: do not use per netns ctl sockets"

This reverts commit a9ef8b25 which is
commit 37ba017d upstream.

It breaks the Android kernel ABI and is not needed for Android devices,
so it is safe to revert for now.  If it is determined that it is needed
in the future, it can be brought back in an abi-preserving way.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ie1e6f2b24c5e360577bc66fde8f969eeea96e99d