LogWriter: setting config must not be abstract

Storing the given config makes sense as default action, no need to
abstract the constructor per default.

refs #7636

library/Icinga/Application/Logger/LogWriter.php

@@ -11,10 +11,18 @@ use Icinga\Application\Config;
  */
 abstract class LogWriter
 {
+    /**
+     * @var Zend_Config
+     */
+    protected $config;
+
     /**
      * Create a new log writer initialized with the given configuration
      */
-    abstract public function __construct(Config $config);
+    public function __construct(Config $config)
+    {
+        $this->config = $config;
+    }
 
     /**
      * Log a message with the given severity