On host interface if a VLAN tagged packet is received, linux kernel removes
the VLAN header from packet byte stream and adds metadata in tpacket2_hdr.
This patch explicitely checks for the presense of VLAN metadata and adds it
in VPP packet.
Change-Id: I0ba35c1e98dbc008ce18d032f22f2717d610c1aa Signed-off-by: Akshaya N <akshaya@rtbrick.com>