The client websocket code will automatically attempt to reconnect on
error or disconnection. This commit:

- Randomises the delay before reconnection
- Wait two seconds before attempting to reconnect (meaning the real
  delay will be between 2 and 4 seconds) -- this is an attempt to spread
  out reconnections over a longer period.
- Makes it stop retrying after 10 attempts (i.e. roughly 30 minutes)