Instead of always mapping the current hostname to 127.0.0.1 or
whatever the user mapped it to manually, make sure the hostname
maps to the default device's IPv4 and IPv6 address if there's
a default device.

This helps out services that do a lookup on the machine hostname
to determine the IP address, which while a broken behavior (since
there are too many edge-cases) is pretty wide-spread and thus
we should support it.