cookie: Stop exporting any-domain cookies

Prior to this change any-domain cookies (cookies without a domain that
are sent to any domain) were exported with domain name "unknown".

Bug: https://github.com/bagder/curl/issues/292

lib/cookie.c

@@ -1277,6 +1277,8 @@ static int cookie_output(struct CookieInfo *c, const char *dumphere)
     co = c->cookies;
 
     while(co) {
+      if(!co->domain)
+        continue;
       format_ptr = get_netscape_format(co);
       if(format_ptr == NULL) {
         fprintf(out, "#\n# Fatal libcurl error\n");
@@ -1310,7 +1312,8 @@ struct curl_slist *Curl_cookie_list(struct SessionHandle *data)
   c = data->cookies->cookies;
 
   while(c) {
-    /* fill the list with _all_ the cookies we know */
+    if(!c->domain)
+      continue;
     line = get_netscape_format(c);
     if(!line) {
       curl_slist_free_all(list);