Werk #5516: cmk-update-agent: Catch HTTPS redirect

A communication between the Agent Updater and the Check_MK-Server won't succeed if the communication protocol is configured to HTTP while the server enforces HTTPS. The reason is that the POST data sent by the Agent Updater will be lost on the redirect.

So far, this is normal HTTP behavior. Nonetheless, the Agent Updater now handles this situation by detecting the redirect and directly sending its data via (unverified) HTTPS.

A warning will therefore be displayed to the user respectively written to log.

To the list of all Werks