When enabled the virtio-net-pci, guest network packet will
load the vnet_hdr. In COLO status, the primary VM's network
packet maybe redirect to another VM, it needs filter-redirect
enable the vnet_hdr flag at the same time, COLO-proxy will
correctly parse the original network packet. If have any
misconfiguration here, the vnet_hdr_len is wrong for parse
the packet, the data+offset will point to wrong place.

Signed-off-by: Zhang Chen <chen.zhang@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>