Subsequent requests in HTTPRequest don't resolve after #49026

[YuriSizov]

Godot version:

master @ 9990f28

OS/device including version:

Windows 10

Issue description:

#49026 breaks file downloading (e.g. export templates downloading in the editor). The download stops at an unassuming status STATUS_DISCONNECTED:

If use_threads is disabled, the status changes to STATUS_RESOLVING, but it still stops at that and never downloads anything.

Code that doesn't work:

	download_templates->set_download_file(EditorPaths::get_singleton()->get_cache_dir().plus_file("tmp_templates.tpz"));
	download_templates->set_use_threads(true);

	Error err = download_templates->request(p_url);

But requests like this do work:

	request_mirror->request("https://godotengine.org/mirrorlist/" + p_version + ".json");

Steps to reproduce:
Build master from 9990f28 with version.py set to a valid stable release, then try to download export templates from the editor. Mirror list is successfully fetched, but file download hangs as described above.

Minimal reproduction project:

Not applicable.

[akien-mga]

CC @sarchar @Faless

[sarchar]

I was able to reproduce this same bug in c5f237e, so I don't think it's related to the DNS request. Nevermind. Looks related to DNS now, something with the mutex lock not being released. On it.

Probably related, if you close the dialog while it says "Disconnected", and then re open the dialog by clicking "Download", the Mirrors list also fails to be retrieved.

Also interesting is that after closing that templates dialog, the editor fails to exit - it seems to lock up as if it's waiting on something (like a background thread that fails to exit?)

[sarchar]

I have a fix and will create a PR shortly.