Automatic merge from submit-queue
Close tunnels after failed healthchecks.
When we fail an ssh-tunnel healthcheck, we currently leak a file descriptor keeping the SSH connection open.
This closes the underlying tunnel before removing our pointer to it. It is possible that the tunnel was functional, but the healthcheck failed for some other reason (e.g. kubelet healthz down), which could close an in-use tunnel, but I think that is acceptable.
Automatic merge from submit-queue
Don't log private SSH key
Log files may have more inclusive permissions than private SSH keys, and as such we should not log the key, even if it looks invalid. I accidentally leaked my key this way when posting e2e test logs.