Fix thread leakage caused by es client connection creation

[YczYanchengzhe]

Since the es plugin creates a connection when acquiring the peer, but does not close it, this will cause thread leakage problems

• If this pull request closes/resolves/fixes an existing issue, replace the issue number. Closes #.
• Update the CHANGES log.

[wu-sheng]

2 things

1. Please fix the code format. Error from the logs.

2021-01-12T11:58:43.9816407Z [INFO] There is 1 error reported by Checkstyle 8.19 with /home/runner/work/skywalking/skywalking/apm-checkstyle/checkStyle.xml ruleset.
2021-01-12T11:58:43.9833897Z [ERROR] src/main/java/org/apache/skywalking/apm/plugin/elasticsearch/v6/interceptor/RestHighLevelClientConInterceptor.java:[35,31] (naming) ConstantName: Name 'logger' must match pattern '(^[A-Z][A-Z0-9](_[A-Z0-9]+)$)'.

2. Please update CHANGES.md in the root folder.

[YczYanchengzhe]

I fixed the problem you mentioned, what should I do next, do I check the ci again~

[codecov]

Codecov Report

Merging #6187 (0d97266) into master (d299ce0) will increase coverage by 2.62%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #6187      +/-   ##
============================================
+ Coverage     46.28%   48.91%   +2.62%     
- Complexity     2553     3317     +764     
============================================
  Files          1690      919     -771     
  Lines         35718    22778   -12940     
  Branches       4138     2220    -1918     
============================================
- Hits          16532    11141    -5391     
+ Misses        18226    10688    -7538     
+ Partials        960      949      -11     

Impacted Files	Coverage Δ	Complexity Δ
...g/oap/server/core/cluster/ClusterHealthStatus.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (ø%)
...ng/apm/agent/core/context/trace/LogDataEntity.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (ø%)
...p/server/core/analysis/metrics/MinLongMetrics.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (ø%)
...er/exporter/provider/grpc/GRPCExporterSetting.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (ø%)
...re/logging/core/converters/AgentNameConverter.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (ø%)
...king/oap/server/configuration/api/ConfigTable.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (ø%)
...skywalking/oap/server/receiver/envoy/als/Role.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (ø%)
...op/server/receiver/mesh/MeshGRPCHandlerCompat.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (-1.00%)
...r/receiver/envoy/als/k8s/ServiceNameFormatter.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (ø%)
...alking/oap/server/core/cluster/OAPNodeChecker.java	0.00% <0.00%> (-93.75%)	0.00% <0.00%> (ø%)
... and 1227 more

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[wu-sheng]

Once plugin test passed, good to merge.