The logic is taken from dump ratelimit: if the config changes, we discard the
counters. This allows the user apply new limits and "start from scratch" in
that case.
This actually makes StartLimitIntervalSec=infinity (or with a large interval)
work as expected, because the counter is maintained even if daemon-reload
operations are interleaved.
In general, it's better to avoid a negation. And "!" is special, because it is
used for history expansion, i.e. the same command would behave differently if
pasted on the command line.
Inspired by 4a899c5a23.
Zbigniew Jędrzejewski-Szmek
Frantisek Sumsal