Daemon Logger: do not override given log level

fixes #2139

doc/82-Changelog.md

@@ -32,6 +32,7 @@ next (will be 1.8.0)
 * FEATURE: Self Service API ignores empty/missing properties (e.g. no address)
 
 ### Background Daemon
+* FIX: Daemon Logger used to not override the given log level (#2139)
 * FEATURE: Daemon: prepare for future reactphp promise versions (#2137)
 
 ### Internals

library/Director/Daemon/Logger.php

@@ -8,12 +8,15 @@ use Icinga\Exception\ConfigurationError;
 
 class Logger extends IcingaLogger
 {
-    public static function replaceRunningInstance(LogWriter $writer, $level = self::DEBUG)
+    public static function replaceRunningInstance(LogWriter $writer, $level = null)
     {
         try {
-            self::$instance
-                ->setLevel($level)
-                ->writer = $writer;
+            $instance = static::$instance;
+            if ($level !== null) {
+                $instance->setLevel($level);
+            }
+
+            $instance->writer = $writer;
         } catch (ConfigurationError $e) {
             self::$instance->error($e->getMessage());
         }