Automatic merge from submit-queue (batch tested with PRs 36419, 38330, 37718, 38244, 38375)

Guarantees drop packets commands succeed in reboot test

Fixes the main case in #33405 and #36230.
Previous attempted fix in #38057.

During the reboot test, the iptables command that was supposed to take the node offline failed to exec. 
Turned out the xtables lock was holding by other processes led to this failure. Logs as below:
```
I1202 20:00:29.686] Dec  2 20:00:29.685: INFO: ssh jenkins@146.148.111.167:22: stdout:
"+ sleep 10
+ sudo iptables -I INPUT 1 -s 127.0.0.1 -j ACCEPT
Another app is currently holding the xtables lock. Perhaps you want to use the -w option?"
I1202 20:00:29.686] Dec  2 20:00:29.685: INFO: ssh jenkins@146.148.111.167:22: stderr:    ""
I1202 20:00:29.686] Dec  2 20:00:29.685: INFO: ssh jenkins@146.148.111.167:22: exit code: 0
```

This reboot test won't pass if any one of these iptables commands fails. This PR put "reboot" commands into while loops to guarantee it retries until succeed.

`sudo iptables -t filter -nL` is removed since it is clear now that the `FILTER` rules won't be clobbered.

(Tests passed on local cluster.)

@bprashanth