If no resolver configuration was found, we would fall back to INADDR_ANY
and IN6ADDR_ANY. This made sense when it was first written thirty or
forty years ago but not today, especially since connecting to INADDR_ANY
or IN6ADDR_ANY is no longer supported. Switch to the loopback address
and simplify the code.

Note that (as the pre-existing comment in the code states) running
without a resolver configuration is not really supported. Still, if
we're going to have a hardcoded fallback, it might as well work.

PR: 291790
MFC after: 1 week