[NET]: Simple ctl_table to ctl_path conversions.

This patch includes many places, that only required
replacing the ctl_table-s with appropriate ctl_paths
and call register_sysctl_paths().

Nothing special was done with them.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>