exponential backoff handling for websocket reconnect

[mahibi]

Websocket retry handling is going wild in some cases.
(also when app is in background, probably because android restricts access in this case).

Errors like these are logged:

HTTP FAILED: java.net.UnknownHostException

WebSocketInstance  com.nextcloud.talk2  E  Error : WebSocket 211756568  java.net.SocketException: Software caused connection abort

There needs to be an exponential backoff handling to not stress the devices.