log: add 'warning' notification when log

- Related Changes for `warning` notification

Add a `bool` type parameter in `log_()` and `lov()`, this `bool` flag
 indicates if we should call `warning` notifier.

1) The process of copying `log_book` of every peer to the `log_book` of
`ld` is usually included in `log_()` and `lov()`, and it may lead to
repeated `warning` notification. So a `bool`, which explicitly indicates
if the `warning` notification is disabled during this call, is necessary
.
2) The `LOG_INFO` and `LOG_DEBUG` level don't need to call
warning, so set that `bool` paramater as `FALSE` for these log level and
only set it as `TRUE` for `LOG_UNUAUSL`/`LOG_BROKEN`. As for `LOG_IO`,
it use `log_io()` to log, so we needn't think about notifier for it.

lightningd/plugin.c

@@ -196,6 +196,7 @@ static void plugin_log_handle(struct plugin *plugin, const jsmntok_t *paramstok)
 {
 	const jsmntok_t *msgtok, *leveltok;
 	enum log_level level;
+	bool call_notifier;
 	msgtok = json_get_member(plugin->buffer, paramstok, "message");
 	leveltok = json_get_member(plugin->buffer, paramstok, "level");
 
@@ -222,7 +223,8 @@ static void plugin_log_handle(struct plugin *plugin, const jsmntok_t *paramstok)
 		return;
 	}
 
-	log_(plugin->log, level, "%.*s", msgtok->end - msgtok->start,
+	call_notifier = (level == LOG_BROKEN || level == LOG_UNUSUAL)? true : false;
+	log_(plugin->log, level, call_notifier, "%.*s", msgtok->end - msgtok->start,
 	     plugin->buffer + msgtok->start);
 }