Tweak rate-limiting

[DL6ER]

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This PR tweaks rate-limiting by ensuring clients are not unblocked after the configured interval if they are continuously querying and, hence, deserve continued blocking.

Interesting side-effect: I forgot about this change, sorry. If we'd have it in the current release, #1197 would not have even happened (it is fixed herein as well, even if differently). Nonetheless, it still makes sense to also merge #1197

[yubiuser]

Works as expected. I've a rate limit of 1000 queries in 60 seconds.

Sending 1000 and than stopping:

[2021-09-22 21:03:24.070 27865M] Rate-limiting 10.0.1.39 for at least 48 seconds
[2021-09-22 21:04:12.756 27865/T27870] Ending rate-limitation of 10.0.1.39

Sending 1000 and than again 1000 while still blocked (within the initial block periode) :

[2021-09-22 21:07:18.510 27865M] Rate-limiting 10.0.1.39 for at least 54 seconds
[2021-09-22 21:08:12.008 27865/T27870] Still rate-limiting 10.0.1.39 as it made additional 1076 queries
[2021-09-22 21:09:12.071 27865/T27870] Ending rate-limitation of 10.0.1.3

Sending 1000 and than again 1000 while still blocked (within the initial block periode) and 1000 in the "still-blocked periode" :

[2021-09-22 21:13:01.541 27865M] Rate-limiting 10.0.1.39 for at least 11 seconds
[2021-09-22 21:13:12.324 27865/T27870] Still rate-limiting 10.0.1.39 as it made additional 1048 queries
[2021-09-22 21:14:12.388 27865/T27870] Still rate-limiting 10.0.1.39 as it made additional 1221 queries
[2021-09-22 21:15:12.451 27865/T27870] Ending rate-limitation of 10.0.1.39

Sending 1000, waiting for 1 minute (getting unblocked) and then immediately sending another 1000

[2021-09-22 21:10:28.018 27865M] Rate-limiting 10.0.1.39 for at least 44 seconds
[2021-09-22 21:11:12.197 27865/T27870] Ending rate-limitation of 10.0.1.39
[2021-09-22 21:11:17.546 27865M] Rate-limiting 10.0.1.39 for at least 55 seconds
[2021-09-22 21:12:12.261 27865/T27870] Ending rate-limitation of 10.0.1.39

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/pi-hole-ftl-v5-11-web-v5-8-and-core-v5-6-released/50566/1