docker: handle leftypol not shipping with instance-config.php

docker/php/bootstrap.sh

@@ -3,10 +3,9 @@
 set -eu
 
 function set_cfg() {
-    if [ -L "/var/www/inc/$1" ]; then
+    if [ ! -f "/var/www/inc/$1" ]; then
         echo "INFO: Resetting $1"
-        rm "/var/www/inc/$1"
-        cp "/code/inc/$1" "/var/www/inc/$1"
+        touch "/var/www/inc/$1"
         chown www-data "/var/www/inc/$1"
         chgrp www-data "/var/www/inc/$1"
         chmod 600 "/var/www/inc/$1"