ipvlan: Scrub skb before crossing the namespace boundry

The earlier patch c3aaa06d

 (ipvlan: scrub skb before routing
in L3 mode.) did this but only for TX path in L3 mode. This
patch extends it for both the modes for TX/RX path.

Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>