fix table name in garbage script

scripts/garbage.pl

@@ -152,7 +152,7 @@ db_log_verbose($dbh,"Remove dup connection $c_id: $c_port_id $c_auth_id");
 }
 
 ##### clean empty user account and corresponded devices ################
-my $u_sql = "SELECT * FROM User_list as U WHERE (User_list.ou_id=".$default_hotspot_ou_id." OR User_list.ou_id=".$default_user_ou_id.") AND (SELECT COUNT(*) FROM User_auth WHERE User_auth.deleted=0 AND User_auth.user_id = U.id)=0";
+my $u_sql = "SELECT * FROM User_list as U WHERE (U.ou_id=".$default_hotspot_ou_id." OR U.ou_id=".$default_user_ou_id.") AND (SELECT COUNT(*) FROM User_auth WHERE User_auth.deleted=0 AND User_auth.user_id = U.id)=0";
 my @u_ref = get_records_sql($dbh,$u_sql);
 foreach my $row (@u_ref) {
 do_sql($dbh,"DELETE FROM User_list WHERE id='".$row->{id}."'");