[fix] Avoid NPE when closing an uninitialized SameAuthParamsLookupAutoClusterFailover

[merlimat]

Motivation

An exception in the PulsarClientImpl constructor will lead to close the SameAuthParamsLookupAutoClusterFailover instance which might not be initialized yet. When it happens it causes an NPE that masks the original exception.

Failed to shutdown Pulsar client @timestamp=2025-01-29T20:21:32.607Z logger-name=org.apache.pulsar.client.impl.PulsarClientImpl thread-name=main level=WARN level-value=30000 stack-trace=`java.lang.NullPointerException: Cannot invoke "org.apache.pulsar.shade.io.netty.util.concurrent.ScheduledFuture.cancel(boolean)" because "this.scheduledCheckTask" is null
        at org.apache.pulsar.client.impl.SameAuthParamsLookupAutoClusterFailover.close(SameAuthParamsLookupAutoClusterFailover.java:111)
        at org.apache.pulsar.client.impl.PulsarClientImpl.shutdown(PulsarClientImpl.java:899)
        at org.apache.pulsar.client.impl.PulsarClientImpl.<init>(PulsarClientImpl.java:265)
        at org.apache.pulsar.client.impl.PulsarClientImpl.<init>(PulsarClientImpl.java:168)
        at org.apache.pulsar.client.impl.ClientBuilderImpl.build(ClientBuilderImpl.java:71)

Modifications

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Codecov Report

Attention: Patch coverage is 42.85714% with 4 lines in your changes missing coverage. Please review.

Project coverage is 74.19%. Comparing base (bbc6224) to head (4a6ac8e).
Report is 877 commits behind head on master.

Files with missing lines	Patch %	Lines
.../impl/SameAuthParamsLookupAutoClusterFailover.java	33.33%	1 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #23911      +/-   ##
============================================
+ Coverage     73.57%   74.19%   +0.61%     
+ Complexity    32624    31843     -781     
============================================
  Files          1877     1853      -24     
  Lines        139502   143738    +4236     
  Branches      15299    16339    +1040     
============================================
+ Hits         102638   106640    +4002     
+ Misses        28908    28683     -225     
- Partials       7956     8415     +459     

Flag	Coverage Δ
inttests	26.77% <0.00%> (+2.18%)	⬆️
systests	23.22% <0.00%> (-1.11%)	⬇️
unittests	73.69% <42.85%> (+0.85%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...rg/apache/pulsar/client/impl/PulsarClientImpl.java	75.12% <100.00%> (+0.81%)	⬆️
.../impl/SameAuthParamsLookupAutoClusterFailover.java	67.07% <33.33%> (ø)

... and 1032 files with indirect coverage changes