Fix issue that causes postfix to not start on systems other than Debian 10

postfix/nullclient/etc/postfix/master.cf

@@ -73,7 +73,10 @@ virtual   unix  -       n       n       -       -       virtual
 lmtp      unix  -       -       y       -       -       lmtp
 anvil     unix  -       -       y       -       1       anvil
 scache    unix  -       -       y       -       1       scache
+{# This is not supported by older postfix versions #}
+{% if grains['oscodename'] == 'buster' %}
 postlog   unix-dgram n  -       n       -       1       postlogd
+{% endif %}
 #
 # ====================================================================
 # Interfaces to non-Postfix software. Be sure to examine the manual