Fix flaky test testGetPropertyNames.

[yyfMichaelYan]

Fix the flaky test testGetPropertyNames due to the non-deterministic iteration order of HashSet.

This flaky test is found by using Nondex, a tool used to find flaky tests in Java projects. The original assertion on Line#69 may fail because the iteration order of HashSet is non-deterministic, and the elements in the array converted from somePropertyNames may not be the same as the array result. By converting result to a HashSet, the new assertion assertEquals will only check the elements are equal in both sets so that the test will always pass.

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[yyfMichaelYan]

I have read the CLA Document and I hereby sign the CLA

[codecov-commenter]

Codecov Report

Merging #4082 (1189252) into master (0e14333) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #4082      +/-   ##
============================================
- Coverage     52.45%   52.39%   -0.06%     
+ Complexity     2612     2609       -3     
============================================
  Files           484      484              
  Lines         15203    15203              
  Branches       1572     1572              
============================================
- Hits           7974     7966       -8     
- Misses         6675     6683       +8     
  Partials        554      554              

Impacted Files	Coverage Δ
...work/apollo/biz/message/DatabaseMessageSender.java	50.00% <0.00%> (-14.59%)	⬇️
.../apollo/internals/RemoteConfigLongPollService.java	77.71% <0.00%> (-0.61%)	⬇️

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[nobodyiam]

Thanks!