net: Kill register_sysctl_rotable

register_sysctl_rotable never caught on as an interesting way to
register sysctls.  My take on the situation is that what we want are
sysctls that we can only see in the initial network namespace.  What we
have implemented with register_sysctl_rotable are sysctls that we can
see in all of the network namespaces and can only change in the initial
network namespace.

That is a very silly way to go.  Just register the network sysctls
in the initial network namespace and we don't have any weird special
cases to deal with.

The sysctls affected are:
/proc/sys/net/ipv4/ipfrag_secret_interval
/proc/sys/net/ipv4/ipfrag_max_dist
/proc/sys/net/ipv6/ip6frag_secret_interval
/proc/sys/net/ipv6/mld_max_msf

I really don't expect anyone will miss them if they can't read them in a
child user namespace.

CC: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_fragment.c

@@ -807,7 +807,7 @@ static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
 
 static void ip4_frags_ctl_register(void)
 {
-	register_net_sysctl_rotable(net_ipv4_ctl_path, ip4_frags_ctl_table);
+	register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
 }
 #else
 static inline int ip4_frags_ns_ctl_register(struct net *net)