We no longer tell the clinet "This is embarrassing..."
when we disconnect and unload an idle document. Instead,
the client UI remains greyed out so the user can resume
as if it was inactive (and reload the document in this case).
Also, we now always send the "close: " message prior
to shutting down a client websocket. This is more
reasonable and consistent when we intentionally disconnect,
so clients can rely on it to signal intent and give reason.
Otherwise, a disconnection without this application-level
message should be unexpected and is therefore reasonable
to show the "This is embarrassing..." message.
Change-Id: Ic7439bcc9267be155586ccd5d122e9fe60225516
0476d1d9f2