rtmp-services: Do not check for valid URL if using "auto"

"Auto" is sort of a special use-case for certain services
(Twitch/Mixer), and the code recently added in be8ddc06a would
unintentionally override it.  This would for example cause the "Auto"
setting on Twitch to set the user to use an Asia server unintentionally
because "auto" is not in the json file.

plugins/rtmp-services/rtmp-common.c

@@ -36,6 +36,8 @@ static void ensure_valid_url(struct rtmp_common *service, json_t *json,
 
 	if (!service->server || !servers || !json_is_array(servers))
 		return;
+	if (astrcmpi(service->server, "auto") == 0)
+		return;
 
 	json_array_foreach (servers, index, server) {
 		const char *url = get_string_val(server, "url");