[#9157] Prevent initializing active thread workers multiple times

[smilu97]

resolves #9157

[codecov]

Codecov Report

Merging #9158 (7f43bde) into master (823b1e0) will increase coverage by 0.15%.
The diff coverage is 77.77%.

@@             Coverage Diff              @@
##             master    #9158      +/-   ##
============================================
+ Coverage     39.61%   39.77%   +0.15%     
- Complexity    11684    11715      +31     
============================================
  Files          3355     3355              
  Lines         90475    90490      +15     
  Branches      10053    10053              
============================================
+ Hits          35846    35993     +147     
+ Misses        51583    51428     -155     
- Partials       3046     3069      +23     

Impacted Files	Coverage Δ
...websocket/ActiveThreadCountResponseAggregator.java	40.76% <77.77%> (+40.76%)	⬆️
...m/navercorp/pinpoint/rpc/client/ConnectFuture.java	70.83% <0.00%> (-8.34%)	⬇️
...vercorp/pinpoint/rpc/packet/ClientClosePacket.java	46.66% <0.00%> (-6.67%)	⬇️
...orp/pinpoint/rpc/server/DefaultPinpointServer.java	78.60% <0.00%> (-2.47%)	⬇️
...avercorp/pinpoint/web/service/SpanServiceImpl.java	0.00% <0.00%> (ø)
...oint/web/websocket/ActiveThreadCountErrorType.java	93.54% <0.00%> (+9.67%)	⬆️
...rp/pinpoint/web/websocket/WorkerActiveManager.java	22.34% <0.00%> (+22.34%)	⬆️
...inpoint/web/websocket/ActiveThreadCountWorker.java	37.50% <0.00%> (+37.50%)	⬆️
...corp/pinpoint/web/cluster/ClusterKeyAndStatus.java	100.00% <0.00%> (+100.00%)	⬆️

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[emeroad]

LGTM