[IPV4]: Incorrect permissions on route flush sysctl

This has been brought up before.. http://lkml.org/lkml/2000/1/21/116
but didnt seem to get resolved.  This morning I got someone
file a bugzilla about it breaking sysctl(8).

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>