supoprt interface options for vxlan, such as df, local_ip and dst_port.

[danieldin95]

Port "vx-100650119"
            Interface "vx-100650119"
                type: vxlan
                options: {df_default="false", dst_port="4789", key=flow, remote_ip="100.65.0.119"}

[franckrupin]

@danieldin95 I fixed the CI, it is merged into master https://github.com/digitalocean/go-openvswitch/pull/108 https://github.com/digitalocean/go-openvswitch/actions/runs/1230468099