Don't create config template if alternate path used
From the documentation, config files in many locations are supported:
These file system paths are searched in the following order to find your site's custom
mailman.cfgfile. The first file found is used.
- The file system path specified by the environment variable
mailman.cfgin the current working directory
var/etc/mailman.cfgrelative to the current working directory
../../etc/mailman.cfgrelative to the working directory of
However, the check before writing the config template only checked if /etc/mailman.cfg existed before writing the template, so the template would always be written for users or alternative config file paths, even when they had existing configurations.