No error message on wrong letsencrypt cache folder

[Benjamin Mugnier]

The new let's encrypt code now use a directory for the cache instead of a single file.

Therefore this line in the config file letsencrypt_cache = letsencrypt.cache from the old version should be changed to something like letsencrypt_cache = ./<folder name> or an error will be printed.

However in this case, no error is printed.
KiwiIRC exists with error code 1, and only print Using config <config file>