Solve the issue sleeping based tests are not stable

[jasonjoo2010]

Describe what this PR does / why we need it

By mock the class TimeUtil we can precisely control the sleep delay.

Not only the tests become stable but they would take less time to finish.

Does this pull request fix one issue?

Resolves #541

[CLAassistant]

All committers have signed the CLA.

[codecov-io]

Codecov Report

Merging #546 into master will increase coverage by 0.25%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #546      +/-   ##
============================================
+ Coverage     37.68%   37.93%   +0.25%     
- Complexity     1102     1109       +7     
============================================
  Files           259      259              
  Lines          8171     8171              
  Branches       1113     1113              
============================================
+ Hits           3079     3100      +21     
+ Misses         4695     4666      -29     
- Partials        397      405       +8

Impacted Files	Coverage Δ	Complexity Δ
...ibaba/csp/sentinel/eagleeye/EagleEyeLogDaemon.java	30.3% <0%> (-15.16%)	6% <0%> (-2%)
...om/alibaba/csp/sentinel/eagleeye/SyncAppender.java	53.57% <0%> (-14.29%)	5% <0%> (-1%)
...a/csp/sentinel/slots/statistic/base/LeapArray.java	65.82% <0%> (-3.8%)	24% <0%> (-1%)
...sentinel/eagleeye/EagleEyeRollingFileAppender.java	28.9% <0%> (-2.32%)	11% <0%> (-1%)
...l/cluster/server/connection/ConnectionManager.java	74% <0%> (-2%)	10% <0%> (-1%)
...a/csp/sentinel/slots/statistic/base/LongAdder.java	31.91% <0%> (+14.89%)	10% <0%> (+6%)	⬆️
...java/com/alibaba/csp/sentinel/log/LoggerUtils.java	66.66% <0%> (+19.99%)	4% <0%> (+2%)	⬆️
...a/csp/sentinel/slots/statistic/base/Striped64.java	60.41% <0%> (+34.37%)	10% <0%> (+5%)	⬆️

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[sczyh30]

Please also reformat the relevant code.

[sczyh30]

LGTM

[sczyh30]

Nice, thanks for contributing!