livekit_signaller: Improved shutdown behavior
Without sending a Leave request to the server before disconnecting, the disconnected client will appear present and stuck in the room for a little while until the server removes it due to inactivity.
After this change, the disconnecting client will immediately leave the room.
This now matches the LiveKit rust SDK implementation at https://github.com/livekit/rust-sdks/blob/418e67c94a066eba91b07c425321102fcd08d167/livekit/src/rtc_engine/rtc_session.rs#L694-L702 .
Edited by Jordan Yelloz