pod-to-internet-connectivity installation check sometimes failed in CI

[tnqn]

Describe the bug

I saw the failure at least twice:
https://github.com/antrea-io/antrea/actions/runs/9461915489/job/26063912880?pr=6427

[kind-kind] -------------------------------------------------------------------------------------------
[kind-kind] Running test: pod-to-internet-connectivity
[kind-kind] -------------------------------------------------------------------------------------------
[kind-kind] Validating connectivity from Pod antrea-test-1m2pj/test-client-84c4bb5558-wswd6 to the world (google.com)...
[kind-kind] /agnhost command '/agnhost connect google.com:80 --timeout=3s' failed: command terminated with exit code 1
[kind-kind] /agnhost stderr: TIMEOUT
[kind-kind] Test pod-to-internet-connectivity failed: Pod antrea-test-1m2pj/test-client-84c4bb5558-wswd6 was not able to connect to google.com: command terminated with exit code 1

agnhost connect only tries to establish TCP connection, not sure why 3s is not enough.

If it keeps failing, maybe we should consider increasing the timeout or switch to another address, like some github service.

[antoninbas]

For what it's worth, I think I saw it failed even back when we had the timeout set to 5s instead of 3s.
We know it's not a DNS issue, as the error message would be different.
It could be some firewall on the Google side. I agree with you, api.github.com may be a good option.