Cacti command injection in cmd_realtime.php

Cacti provides an operational monitoring and fault management framework. A command injection vulnerability on the 1.3.x DEV branch allows any unauthenticated user to execute arbitrary command on the server when `register_argc_argv` option of PHP is `On`. In `cmd_realtime.php` line 119, the `$poller_id` used as part of the command execution is sourced from `$_SERVER['argv']`, which can be controlled by URL when `register_argc_argv` option of PHP is `On`. And this option is `On` by default in many environments such as the main PHP Docker image for PHP. Commit 53e8014d1f082034e0646edc6286cde3800c683d contains a patch for the issue, but this commit was reverted in commit 99633903cad0de5ace636249de16f77e57a3c8fc.