Chain Service de-syncs from tip

[dangeross]

The electrum client keeps sync with the latest headers by subscribing to header events. The lwk_wollet uses this to get the tip when needed. But if the underlying stream is not used regularly the stream connection is dropped by the remote. Because of the way lwk_wollet is initialised it only subscribes to header events once, if the connection is dropped the tip de-syncs as no new header events come in (not being re-subscribed on reconnect)

bitcoindevkit/rust-electrum-client#124

[dangeross]

Closed by #315