test: assume no IPv6 if interfaces cannot be listed

PR-URL: libuv#724
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>

Author: ujsxn

test/task.h

@@ -207,7 +207,7 @@ UNUSED static int can_ipv6(void) {
   int i;
 
   if (uv_interface_addresses(&addr, &count))
-    return 1;  /* Assume IPv6 support on failure. */
+    return 0;  /* Assume no IPv6 support on failure. */
 
   supported = 0;
   for (i = 0; supported == 0 && i < count; i += 1)