Always call res_init() before getaddrinfo().

Unfortunately, glibc assumes that /etc/resolv.conf is a static file that
never changes. Even on servers, /etc/resolv.conf might be a dynamically
generated file, and we never know when it changes. So just call
res_init() every time, so glibc uses up-to-date nameserver information.

src/net_setup.c

@@ -663,6 +663,9 @@ static bool add_listen_address(char *address, bool bindto) {
 	hint.ai_protocol = IPPROTO_TCP;
 	hint.ai_flags = AI_PASSIVE;
 
+#ifdef HAVE_DECL_RES_INIT
+	res_init();
+#endif
 	int err = getaddrinfo(address && *address ? address : NULL, port, &hint, &ai);
 	free(address);