title: multiple toml file not recognised for [file] backend
body: <p>I have simple toml configuration file</p>
  
  <pre><code>    defaultEntryPoints = ["http"]
      logLevel = "DEBUG"
      debug = true
      [entryPoints]
        [entryPoints.http]
        address = ":80"
  
      [file]
       directory = "/etc/traefik/rules.d/"
       watch = true
  </code></pre>
  
  <p>the toml files inside rules.d/ are not recognised nor loaded, I am using latest docker build of traefik. If I use filename instead of directory, it works.</p>