Bug#1106740: postfix: cyrus_sasl_config_path needs to be set explicitly for trixie (not needed for older debian releases)

[Joachim Herb]

> So, what is your point?
1. There seems to be a breaking change between the different 
distribution version => Either keep the existing behavior or add 
documentation somewhere.
2. People, who run into the same problem might find this bug report and 
do not need to spend hours on trying to finger out, what is the problem.