keep country_osm_grid table when dropping update tables

lib/setup/SetupClass.php

@@ -690,7 +690,8 @@ class SetupFunctions
                         'new_query_log',
                         'spatial_ref_sys',
                         'country_name',
-                        'place_classtype_*'
+                        'place_classtype_*',
+                        'country_osm_grid'
                        );
 
         $aDropTables = array();