Failed to set IPv6 DNS with systemd-resolved

IPv6 DNS is not supported in vpnc-script when using systemd-resolved. When receiving multiple DNS servers (IPv4 and IPv6), they are both stored in INTERNAL_IP4_DNS env var, however, calls made to busctl to configure systemd-resolved are enforced to IPv4 address family, and logically fail.

sample logs from vpnc-script

+ busctl call org.freedesktop.resolve1 /org/freedesktop/resolve1 org.freedesktop.resolve1.Manager SetLinkDNS 'ia(iay)' 38 2 2 4 10 1 8 53 2 4 fd03:1::1
Failed to parse 'fd03:1::1' as byte (unsigned 8bit integer): Invalid argument