fix(6509): improve the test case coverage of saga module to 70%

[xjlgod]

• [ ] I have registered the PR changes.

Ⅰ. Describe what this PR did

fix https://github.com/apache/incubator-seata/issues/6509

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[slievrly]

@xjlgod You can submit your PR in stages.

[xjlgod]

@xjlgod You can submit your PR in stages.

I am trying to invoke codecov action to see my test case coverage by add new commit. But I find the error is

'Rate limit reached. Please upload with the Codecov repository upload token to resolve issue. Expected time to availability: 2244s.

It seems that the quota limit has been reached.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 50.24%. Comparing base (933b492) to head (fe9e68d). Report is 27 commits behind head on 2.x.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #6519      +/-   ##
============================================
- Coverage     51.13%   50.24%   -0.89%     
- Complexity     5317     5596     +279     
============================================
  Files           950     1023      +73     
  Lines         33448    35440    +1992     
  Branches       4048     4216     +168     
============================================
+ Hits          17103    17808     +705     
- Misses        14666    15867    +1201     
- Partials       1679     1765      +86     

see 121 files with indirect coverage changes