cdc: fix server etcd may nil by create a new local client. (#2161)

[ti-chi-bot]

This is an automated cherry-pick of #2161

What problem does this PR solve?

server etcdclient may be nil, fix it by create one.

What is changed and how it works?

Check List

Tests

• No code

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch

Release note

• No release note

[3AceShowHand]

/run-all-tests

[amyangfei]

/run-all-tests

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-5.0@0fc7522). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff                @@
##             release-5.0      #2166   +/-   ##
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  Coverage               ?   52.4011%           
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  Files                  ?        164           
  Lines                  ?      17679           
  Branches               ?          0           
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  Hits                   ?       9264           
  Misses                 ?       7424           
  Partials               ?        991           

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• amyangfei
• leoppro

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[zier-one]

/merge

[ti-chi-bot]

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

Commit hash: 0705bfe

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

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[3AceShowHand]

/run-integration-tests

[3AceShowHand]

/run-leak-tests