ofctl_v1_2/3: fix POP_MPLS action and some match fields

The following action and match field causes an error at mod_flow_entry command.

  - ofctl_v1_2.py
    * action: POP_MPLS
    * match field: metadata, mpls_label, ipv6_nd_target

  - ofctl_v1_3.py
    * action: POP_MPLS
    * match field: in_phy_port, ipv6_nd_target

this patch fixes them.

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