title: ValueError: Duplicate plugins for name projector
body: <p>Running <code>tensorboard --logdir log_dir</code> I get an error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/home/user/.local/bin/tensorboard", line 11, in &lt;module&gt;
      sys.exit(run_main())
    File "/home/user/.local/lib/python3.6/site-packages/tensorboard/main.py", line 64, in run_main
      app.run(tensorboard.main, flags_parser=tensorboard.configure)
    File "/home/user/.local/lib/python3.6/site-packages/absl/app.py", line 300, in run
      _run_main(main, args)
    File "/home/user/.local/lib/python3.6/site-packages/absl/app.py", line 251, in _run_main
      sys.exit(main(argv))
    File "/home/user/.local/lib/python3.6/site-packages/tensorboard/program.py", line 228, in main
      server = self._make_server()
    File "/home/user/.local/lib/python3.6/site-packages/tensorboard/program.py", line 309, in _make_server
      self.assets_zip_provider)
    File "/home/user/.local/lib/python3.6/site-packages/tensorboard/backend/application.py", line 161, in standard_tensorboard_wsgi
      reload_task)
    File "/home/user/.local/lib/python3.6/site-packages/tensorboard/backend/application.py", line 194, in TensorBoardWSGIApp
      return TensorBoardWSGI(plugins, path_prefix)
    File "/home/user/.local/lib/python3.6/site-packages/tensorboard/backend/application.py", line 245, in __init__
      raise ValueError('Duplicate plugins for name %s' % plugin.plugin_name)
  ValueError: Duplicate plugins for name projector
  </code></pre>
  
  <p>What can be a reason of this problem?</p>