Fix #4808 Load the existing keys without new line, so array_search can find the old ones. Unset a key from existing_keys only if a match is false and avoid false being treated as 0

Fixed a problem that caused the creation of mysql users to fail. This affected the dev branch only and not the stable 3.1.6 release.

Change check order for welcome-email template. First it should use specific welcome messages for the domain (html before text) and than language specific templates. Otherwise it would use a german html language file before a domain specific text file if html file does not exist.

use seperate config for amavis-dkim-config even is the systems uses a monolith config to prevent overwriting the key-config during updates