ofctl_v1_2/3: support setting the oxm_value to OFPVID_NONE

ofctl_v1_2/3 is now enabled to setting the oxm_value
to OFPVID_NONE(0x0000) as follows:

  curl -X POST -d '{"dpid": 3,
                    "actions":[{"port":2, "type":"OUTPUT"}],
                    "match":{"dl_vlan_none":0}}' http://localhost:8080/stats/flowentry/add

  or

  curl -X POST -d '{"dpid": 3,
                    "actions":[{"port":2, "type":"OUTPUT"}],
                    "match":{"vlan_vid_none":0}}' http://localhost:8080/stats/flowentry/add

Signed-off-by: Minoru TAKAHASHI <takahashi.minoru7@gmail.com>