Fix flaky PinotTenantRestletResourceTest

[Jackie-Jiang]

Another attempt of fixing #11329

Do not add fake instances which connect to the cluster, but only add instance configs. They serve the same way for testing purpose, but fake instances can cause side effect on other tests

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1ab9e62) 61.63% compared to head (cd18c72) 34.92%.
Report is 5 commits behind head on master.

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #12019       +/-   ##
=============================================
- Coverage     61.63%   34.92%   -26.72%     
=============================================
  Files          2385     2309       -76     
  Lines        129271   125576     -3695     
  Branches      20016    19464      -552     
=============================================
- Hits          79682    43854    -35828     
- Misses        43792    78598    +34806     
+ Partials       5797     3124     -2673     

Flag	Coverage Δ
custom-integration1	?
integration	0.00% <0.00%> (-0.01%)	⬇️
integration1	?
integration2	0.00% <0.00%> (ø)
java-11	?
java-21	34.92% <100.00%> (-26.59%)	⬇️
skip-bytebuffers-false	?
skip-bytebuffers-true	34.92% <100.00%> (-26.56%)	⬇️
temurin	34.92% <100.00%> (-26.72%)	⬇️
unittests	46.78% <100.00%> (-14.86%)	⬇️
unittests1	46.78% <100.00%> (-0.21%)	⬇️
unittests2	?

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