flaky test: test_download_via_relay_with_discovery

[Frando]

test_download_via_relay_with_discovery failed with Error: Failed to complete download

https://github.com/n0-computer/iroh/actions/runs/9774608684/job/26983236863#step:10:1485

Marked as flaky in #2450

[Frando]

The failure is here: https://github.com/n0-computer/iroh/blob/main/iroh/src/node.rs#L658

       let hash = node1.blobs().add_bytes(b"foo".to_vec()).await?.hash;

        // create a node addr with node id only
        let addr = NodeAddr::new(node1.node_id());
        node2.blobs().download(hash, addr).await?.await?;

I don't see a reason immediately why this may be flaky. There's no timeout, it uses a local relay, and the operation should be totally predictable. Maybe something about the timings about spawning and discovery being ready?