Use traefik 1.7.17 because the latest 2.0 is not yet compatible

Traefik.php

@@ -49,7 +49,7 @@ class Traefik {
         'version' => '3',
         'services' => [
           'traefik' => [
-            'image' => 'traefik',
+            'image' => 'traefik:1.7.17',
             'restart' => 'unless-stopped',
             'command' => '-c /dev/null --web --docker --logLevel=DEBUG',
             'networks' => [],