If the client cancelled a file upload in the initial callback,
we would incorrectly proceed with the handshake.

This avoids issues with autoplay being disabled.

We already had a server-side timeout, but it didn't prevent
a client from hanging when it lost connectivity with the server.

The ServerConnection.connect method is no longer async,
we rely on the onconnected callback only.  The onconnected
callback is now only called after the initial handshake
completes.  There is a new onerror callback.

We could previously attempt to display a remote stream before
reflectSetting initialised the settings.

Fortunately we're not using the mistyped arguments.

NotAuthorisedError may unwrap to os.ErrNotExist.

Recent versions of Go do it at startup, so only print
a warning if the limit is too low.

Also fix return code in WHIP.

The group and name are in the path, this avoids redundancies.

It was only being enforced in the client.