iface address detection fails to discard ULA addresses

[pelzvieh]

Specifying
iface = <interface name>
for address detection with an IPv6 provider catches a Unique Local Address (fd??:*) associated with the given interface. As the purpose of inadyn usually would be used to set domain names correctly for external access, and ULA are not reachable from outside of its local network, I would regard this to be a bug.

Example context

Configuration iface=wlan0
Interface state:

 wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::affe  prefixlen 64  scopeid 0x20<link>
        inet6 fdab::affe  prefixlen 64  scopeid 0x0<global>
        inet6 2abc::affe  prefixlen 64  scopeid 0x0<global>

Current behaviour in the example

inadyn would pick fdab:::affe as address of interface and set the AAAA record with the configure provider. This is a ULA, not reachable from site-external internet.

Expected behaviour in the example

inady must pick 2abc::affe as address of interface and set the AAAA record with the configure provider to that address.