CluConnection fails if tron shuts down

[albireox]

Reported by @johndonor3, if tron shuts down while TronConnection is connected, the client receives a ton of [WARNING]: Cannot parse errors.

I'm not sure what lines the client would be receiving in this case, bit it's probably an issue with parse_reply. If the line failst o be parsed we should check if the connection is still open and, if not, stop the parsing task.