Add handle return

Fixes the bug that occurred when the handle is initialized at the time of
writing.
The write function uses the return of the open function, but the open
function does not return anything.

Log/Engine/LogstashLog.php

@@ -82,6 +82,7 @@ public function config($config = array()) {
  */
 	protected function _open($host, $port, $timeout) {
 		$handle = pfsockopen($host, $port, $errNo, $errSt, $timeout);
+		return $handle;
 	}
 
 /**