[Bug] Capture curl errors when offline

[alexjustesen]

📃 Description

This PR fixes capturing curl errors when calling a URL especially when offline.

• closes Test status "Started" instead of "Failed" when there is no internet connection #1821
• closes Speedtest stuck in "Started" when can't reach icanhazip.com #1824

🪵 Changelog

➕ Added

• note to docs (https://docs.speedtest-tracker.dev/help/faqs#adguard-and-pi-hole-allow-domains) that https://icanhazip.com/ needs to be added to your allow lists in AdGuard and Pi-hole.

🔧 Fixed

• correctly capture errors when attempting to curl a URL for results.