Prioritize kubernetes routes by path length

The Kubernetes provider wasn't setting priorities which was causing
shorter paths to get chosen before longer ones. This now matches the
[documentation](https://github.com/containous/traefik/blob/master/docs/basics.md#priorities)

templates/kubernetes.tmpl

@@ -9,6 +9,7 @@
 [frontends]{{range $frontendName, $frontend := .Frontends}}
   [frontends."{{$frontendName}}"]
   backend = "{{$frontend.Backend}}"
+  priority = {{$frontend.Priority}}
   passHostHeader = {{$frontend.PassHostHeader}}
     {{range $routeName, $route := $frontend.Routes}}
     [frontends."{{$frontendName}}".routes."{{$routeName}}"]