Fix hookOnCancel handing logic in SentinelReactorSubscriber

[sczyh30]

Describe what this PR does / why we need it

Fix the hookOnCancel handing logic in SentinelReactorSubscriber to avoid Entry-exit leaking.

Does this pull request fix one issue?

Fixes #1084

Describe how you did it

Add tryCompleteEntry() in hookOnCancel hook of SentinelReactorSubscriber.

Note that this is only a temporary solution. We might need to improve or refactor the SentinelReactorSubscriber later to handle all events more appropriately according to the reactive stream specification.

Describe how to verify it

Run the test cases.

Special notes for reviews

NONE

[codecov-io]

Codecov Report

Merging #1089 into master will increase coverage by 0.08%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #1089      +/-   ##
============================================
+ Coverage      42.7%   42.78%   +0.08%     
- Complexity     1491     1493       +2     
============================================
  Files           319      319              
  Lines          9378     9379       +1     
  Branches       1279     1279              
============================================
+ Hits           4005     4013       +8     
+ Misses         4878     4872       -6     
+ Partials        495      494       -1

Impacted Files	Coverage Δ	Complexity Δ
...nel/adapter/reactor/SentinelReactorSubscriber.java	86.88% <100%> (+6.88%)	21 <1> (+2)	⬆️
.../slots/block/flow/controller/WarmUpController.java	78.84% <0%> (-3.85%)	10% <0%> (-1%)
...a/csp/sentinel/slots/statistic/base/LeapArray.java	67.32% <0%> (-2.98%)	33% <0%> (-1%)
...tinel/slots/block/flow/param/ParamFlowChecker.java	55.4% <0%> (+2.7%)	29% <0%> (+1%)	⬆️
...p/sentinel/datasource/consul/ConsulDataSource.java	69.56% <0%> (+4.34%)	7% <0%> (ø)	⬇️
...ava/com/alibaba/csp/sentinel/node/ClusterNode.java	100% <0%> (+4.76%)	8% <0%> (+1%)	⬆️

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[ghost]

LGTM