[Compose] New images with LOG_LINES

[Update] Do not add empty line in each loop

data/Dockerfiles/dovecot/syslog-ng.conf

@@ -35,7 +35,7 @@ destination d_redis_cleanup {
     host("redis-mailcow")
     persist-name("redis3")
     port(6379)
-    command("LTRIM" "DOVECOT_MAILLOG" "0" "9999")
+    command("LTRIM" "DOVECOT_MAILLOG" "0" "`LOG_LINES`")
   );
 };
 filter f_mail { facility(mail); };