Fix logic of StatisticNode#maxSuccessQps

[fangwentong]

Describe what this PR does / why we need it

StatisticNode#maxSuccessQps returns maxSuccess of sliding windows, it should divide the window's interval to get correct QPS result

Does this pull request fix one issue?

Describe how you did it

Describe how to verify it

Special notes for reviews

[claassistantio]

All committers have signed the CLA.

[codecov-io]

Codecov Report

Merging #1196 into master will increase coverage by 0.08%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##             master   #1196      +/-   ##
===========================================
+ Coverage     43.01%   43.1%   +0.08%     
- Complexity     1570    1572       +2     
===========================================
  Files           337     337              
  Lines          9877    9878       +1     
  Branches       1332    1332              
===========================================
+ Hits           4249    4258       +9     
+ Misses         5100    5094       -6     
+ Partials        528     526       -2

Impacted Files	Coverage Δ	Complexity Δ
...a/com/alibaba/csp/sentinel/node/StatisticNode.java	55.55% <100%> (+0.49%)	28 <1> (+1)	⬆️
...tinel/slots/block/flow/param/ParamFlowChecker.java	55.4% <0%> (+2.02%)	29% <0%> (ø)	⬇️
...ava/com/alibaba/csp/sentinel/node/ClusterNode.java	100% <0%> (+3.44%)	11% <0%> (+1%)	⬆️
...p/sentinel/datasource/consul/ConsulDataSource.java	69.56% <0%> (+5.79%)	7% <0%> (ø)	⬇️

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[sczyh30]

Could you please sign the CLA here: https://cla-assistant.io/alibaba/Sentinel?pullRequest=1196

[fangwentong]

@sczyh30 CLA signed

[sczyh30]

LGTM

[sczyh30]

Thanks for contributing!