Automatic merge from submit-queue
Adds termination hook in reboot test for debugging
From #33405 and #36230.
Logs the SSH command issued for dropping inbound / outbound traffic to file and dump it out when test ends.
The first `sudo iptables -t filter -nL` is called to confirm the rules are injected. The second `sudo iptables -t filter -nL` is to check whether the rules get clobbered. Adds `date` in between to check time frame.
@bprashanth @freehan
069c263abd