set CONST_LibDir directly from the source scripts

Now that the source scripts have been moved to \lib, they
can determine the position of the PHP library relative to
themselves.

lib/admin/check_import_finished.php

@@ -1,4 +1,5 @@
 <?php
+@define('CONST_LibDir', dirname(dirname(__FILE__)));
 
 require_once(CONST_LibDir.'/init-cmd.php');
 
@@ -18,7 +19,6 @@ $print_fail = function ($message = 'Failed') use ($term_colors) {
     echo $term_colors['red'].$message.$term_colors['normal']."\n";
 };
 
-
 $oDB = new Nominatim\DB;