Allow listen.ipaddr to reference an IPv6-only host

In 5452b13, these lines were added
which effectively result in a listen.ipaddr only allowing hostnames to
resolve to IPv4 addresses. With a hostname with only a IPv6 address,
it'll bail with the error message:

radiusd: #### Opening IP addresses and Ports ####
listen {
        type = "auth"
Failed resolving "ipv6.cipherboy.com" to IPv4 address:
    Name or service not known

This directly contradicts the language in the default configuration
file, so support resolving both IPv4-only and IPv6-only hostnames.

Signed-off-by: Alexander Scheel <ascheel@redhat.com>

src/lib/misc.c

@@ -607,13 +607,6 @@ int fr_pton(fr_ipaddr_t *out, char const *value, ssize_t inlen, int af, bool res
 			fr_strerror_printf("Invalid address");
 			return -1;
 		}
-
-		/*
-		 *	Fall through to resolving the address, using
-		 *	whatever address family they prefer.  If they
-		 *	don't specify an address family, force IPv4.
-		 */
-		if (af == AF_UNSPEC) af = AF_INET;
 	}
 
 	/*