websocketproxy: remove leftover debug output

Someone reported the following very long entry in their
/var/log/messages:

  Jun  6 15:00:16 gprfc041 nova-novncproxy: }}>>{<{<}>{<{<}> [...]

It turns out that this is from some debug code left in this module.
Just drop it.

Change-Id: I392f599e81790376dab11f9323430ee9abcff444
Merge "websocketproxy: remove leftover debug output"