server(cdc): avoid printing help messages when cdc server exits

[crelax]

What problem does this PR solve?

Issue Number: close #5519

What is changed and how it works?

In func RunE() of the cdc server command, if no error occurs in the validation, return nil directly in spite of errors thrown by the execution. Handle the execution errors using cobra.CheckErr()

Tests

• Integration test
  • tests/integration_tests/cdc_server_tips: The tests cover two scenarios: one cdc server command with invalid arguments should print usage tips, while the other is validated and should not.
• Manual test
  • Start a tidb cluster and add a cluster using cdc server
  • Create a changefeed task using cli changefeed
  • Press Ctrl + C and in the terminal of cdc server and check whether there are prompt messages printed

Will it cause performance regression or break compatibility?

No

Do you need to update user documentation, design documentation or monitoring documentation?

No

Release note

Clear redundant cdc server prompt in a normal exit

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• 3AceShowHand
• liuzix

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[crelax]

/run-check-issue-triage-complete

[codecov-commenter]

Codecov Report

Merging #5524 (8a1a011) into master (fcea4d5) will increase coverage by 0.1679%.
The diff coverage is 60.3387%.

Flag	Coverage Δ
cdc	61.5694% <62.0865%> (+0.4213%)	⬆️
dm	52.0497% <56.4728%> (+0.0070%)	⬆️

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

@@               Coverage Diff                @@
##             master      #5524        +/-   ##
================================================
+ Coverage   56.0768%   56.2448%   +0.1679%     
================================================
  Files           535        527         -8     
  Lines         70143      69866       -277     
================================================
- Hits          39334      39296        -38     
+ Misses        27078      26846       -232     
+ Partials       3731       3724         -7     

[sre-bot]

All committers have signed the CLA.

[liuzix]

/run-integration-tests

[crelax]

/run-verify-test

[crelax]

/run-all-tests

[3AceShowHand]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 8a1a011

[crelax]

/run-verify-test

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #5604.