Ignore RejectedExecutionException if executor is shutdown during submit task

[AlbumenJ]

…it task

What is the purpose of the change?

Checklist

• Make sure there is a GitHub_issue field for the change.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Make sure gitHub actions can pass. Why the workflow is failing and how to fix it?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 60.74%. Comparing base (22395f8) to head (480bdac).
Report is 30 commits behind head on 3.3.

Files with missing lines	Patch %	Lines
.../common/threadpool/serial/SerializingExecutor.java	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##                3.3   #15122   +/-   ##
=========================================
  Coverage     60.73%   60.74%           
- Complexity    10861    10868    +7     
=========================================
  Files          1882     1883    +1     
  Lines         86007    86012    +5     
  Branches      12886    12888    +2     
=========================================
+ Hits          52236    52244    +8     
+ Misses        28326    28322    -4     
- Partials       5445     5446    +1     

Flag	Coverage Δ
integration-tests	33.00% <33.33%> (+<0.01%)	⬆️
samples-tests	29.20% <0.00%> (+0.02%)	⬆️
unit-tests	58.88% <33.33%> (-0.01%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[AlbumenJ]

@EarthChen @icodening @oxsean PTAL

[icodening]

LGTM