Fix new pool url detection

[felixbrucker]

https://github.com/Chia-Network/chia-blockchain/pull/17384 introduced a new feature which updates the pool url in the config file, if a change is detected. This however always triggered (bug), but only updated the config if the url actually differed.

With the addition of https://github.com/Chia-Network/chia-blockchain/pull/18341 an error log line was (incorrectly) added, which made this bug visible, as currently the only use of the function should always produce a config update (but that does not need to be the case).

This PR fixes the bug and removes the incorrect error log line, any errors in the closure are caught by the try/except block. If we want to log whether the config entry was found we need another variable to keep track of that, as updated is not suitable for that.