update vlan_offset in case of QinQ and vlan offload in the same way the parser does
update vlan_offset in case of QinQ and vlan offload in the same way the parser does

ntop/PF_RING,ntop/PF_RING,ntop/PF_RING,ntop/PF_RING,ntop/PF_RING,ntop/PF_RING,ntop/PF_RING