hack/test: make tcp-timeout test portable

At least on Linux nc does not automatically close the sending side of
the connection when the receiving side is closed by yawol. Extend the
test to send a message after the idle timeout to trigger a forceful
close of the sending side of the connection.

hack/tests/README.md

@@ -49,11 +49,17 @@ echo "test"  | nc -u $(kubectl get services udp-timeout --output jsonpath='{.sta
 
 ## tcp-timeout
 
-This command should be closed in 10 sec
+This command should be closed with no output in approximately 10 sec
+
+Bash:
 ```
-time nc $(kubectl get services tcp-timeout --output jsonpath='{.status.loadBalancer.ingress[0].ip}') 80
+time nc $(kubectl get services tcp-timeout --output jsonpath='{.status.loadBalancer.ingress[0].ip}') 80 < <( sleep 11; echo "test" )
 ```
 
+Zsh:
+```
+{ sleep 11; echo "test" } | time nc $(kubectl get services tcp-timeout --output jsonpath='{.status.loadBalancer.ingress[0].ip}') 80
+```
 
 ## cleanup