adapt gateway selection

adapt eip-service.json parsing, if we agree on option 2 in leap/container-platform/glue#12 - ip_address needs to be interpreted as array
prefer ipv6 over ipv4: try to connect to ipv6 first, fall back to ipv4 if the former fails
it seems openvpn 2.4 is able to handle a dual-stack setup, so maybe there's not much to do for checkbox 2. See https://wiki.archlinux.org/index.php/OpenVPN#Connect_to_the_server_via_IPv6, https://serverfault.com/questions/651832/openvpn-with-mixed-ipv4-and-ipv6-clients

Edited Feb 06, 2021 by cyberta

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