Add curl options to allow running check_opcache by Nagios agents

[gfernandez598]

Hi,
Trying to perform opcache checks using Nagios agents running on the same server as PHP/Moodle, we come across a situation where the site/Moodle runs behind a proxy which is the only place where the domain certificates are located, so we must be able to ignore or trust the local server certificates. Also, the certificates may not match the domain name/local site where the Nagios agent wants to perform the check.

This PR attempts to solve the described situations adding optional parameters to the cli/check_opcache.php
An example to test it.
sudo -u www-data /usr/bin/php admin/tool/cli/check_opcache.php ". "--url=\"https://127.0.0.1/admin/tool/opcache/cli/check_opcache_web.php\" --domain=example.com --warning=75 --critical=85 --insecure