Some places, that deal with IP statistics already have where to
get a struct net from, but use it directly, without declaring
a separate variable on the stack.

So, save this net on the stack for future IP_XXX_STATS macros.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>