apps: Use the first detected address family if IPv6 is not available

apps: Use the first detected address family if IPv6 is not available

This is a follow up of 15729bef385211bc2a0497e2d53a45c45d677d2c.  Even
when the host does not support IPv6 at all, BIO_lookup_ex may now
return IN6ADDR_ANY in addition to INADDR_ANY, as the second element of
the ai_next field.

After eee8a40aa5e06841eed6fa8eb4f6109238d59aea, the do_server function
prefers the IPv6 address and fails on the BIO_socket call.  This adds
a fallback code to retry with the IPv4 address returned as the first
element to avoid the error.

The failure had been partially avoided in the previous code with
AI_ADDRCONFIG, because getaddrinfo returns only IPv4 address if no
IPv6 address is associated with external interface.  However, it would
be still a problem if the external interface has an IPv6 address
assigned, while the loopback interface doesn't.

Signed-off-by: Daiki Ueno <dueno@redhat.com>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16074)