fix(network): don't assume prefix length 64 by default

Assuming a default prefix length of 64 by default if no explicit
prefix length is given is wrong and known to cause connectivity
problems in some networks. A prefix length of 128 should be assumed
in this case.

See https://www.rfc-editor.org/rfc/rfc5942 (specifically section 5)
    https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=684009

modules.d/40network/net-lib.sh

@@ -311,7 +311,7 @@ ibft_to_cmdline() {
                 [ -e "${iface}"/hostname ] && read -r hostname < "${iface}"/hostname
                 if [ "$family" = "ipv6" ]; then
                     if [ -n "$ip" ]; then
-                        [ -n "$prefix" ] || prefix=64
+                        [ -n "$prefix" ] || prefix=128
                         ip="[${ip}]"
                         mask=$prefix
                     fi