Remove redundant 'get' action after calling 'computeIFAbsent' on a ConcurrentHashMap.

[JasmineJ1230]

What is the purpose of the change

see #8259

Brief changelog

Remove redundant 'get' action after calling 'computeIFAbsent' on a ConcurrentHashMap.

Verifying this change

Checklist

• Make sure there is a GitHub_issue field for the change (usually before you start working on it). Trivial changes like typos do not require a GitHub issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Check if is necessary to patch to Dubbo 3 if you are work on Dubbo 2.7
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Add some description to dubbo-website project if you are requesting to add a feature.
• GitHub Actions works fine on your own branch.
• If this contribution is large, please follow the Software Donation Guide.

[codecov-commenter]

Codecov Report

Merging #8260 (8aaed4f) into 3.0 (e321324) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##                3.0    #8260      +/-   ##
============================================
- Coverage     63.97%   63.96%   -0.01%     
- Complexity      312      313       +1     
============================================
  Files          1073     1073              
  Lines         45229    45227       -2     
  Branches       6816     6816              
============================================
- Hits          28933    28931       -2     
- Misses        13077    13080       +3     
+ Partials       3219     3216       -3     

Impacted Files	Coverage Δ
...pache/dubbo/config/utils/ReferenceConfigCache.java	62.50% <100.00%> (-0.84%)	⬇️
...ng/transport/dispatcher/all/AllChannelHandler.java	82.75% <0.00%> (-13.80%)	⬇️
...ubbo/registry/client/AbstractServiceDiscovery.java	87.50% <0.00%> (-12.50%)	⬇️
...rg/apache/dubbo/rpc/protocol/dubbo/DubboCodec.java	63.39% <0.00%> (-3.58%)	⬇️
...he/dubbo/registry/multicast/MulticastRegistry.java	66.66% <0.00%> (-1.86%)	⬇️
...apache/dubbo/common/extension/ExtensionLoader.java	80.80% <0.00%> (+0.21%)	⬆️
...n/java/org/apache/dubbo/common/utils/NetUtils.java	67.68% <0.00%> (+0.34%)	⬆️
...figcenter/file/FileSystemDynamicConfiguration.java	59.52% <0.00%> (+0.47%)	⬆️
...ava/org/apache/dubbo/common/utils/ConfigUtils.java	70.12% <0.00%> (+0.60%)	⬆️
...etadata/report/support/AbstractMetadataReport.java	61.72% <0.00%> (+0.95%)	⬆️
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e321324...8aaed4f. Read the comment docs.