Revert "ipv4: shrink netns_ipv4 with sysctl conversions"

This reverts commit f662a078 which is
commit 4b6bbf17 upstream.

It breaks the Android kernel abi, and is not needed at this point in
time.  If it is required, it can come back in an ABI-safe way.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I762a8a7eaee1baa7dbedc9c72854b85cfffbe7d9