Report delayed errors

[sfan5]

fixes #65

note: I am running this in prod, just want to keep an eye on bugs before merging.

[sfan5]

how it looks on the client:

2024-10-13 10:27:16: ACTION[Server]: Announcing start to servers.minetest.net
2024-10-13 10:32:16: ERROR[CurlFetch]: HTTPFetch for servers.minetest.net/announce returned response code 409
2024-10-13 10:32:16: ERROR[CurlFetch]: Response body:
2024-10-13 10:32:16: ERROR[CurlFetch]: Request has been filed, but the previous request encountered the following error:
2024-10-13 10:32:16: ERROR[CurlFetch]: Server x.x.x.x port 30000 did not respond to ping