pd_client: reconnect leader only when members change (#9788)

[ti-srebot]

cherry-pick #9788 to release-4.0
You can switch your code base to this Pull Request by using git-extras:

# In tikv repo:
git pr https://github.com/tikv/tikv/pull/9818

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tikv.git pr/9818:release-4.0-c4003abeba0f

---

What problem does this PR solve?

Issue Number: close #9690

What's Changed:

Reconnecting leader only when members change to avoid disturbing heartbeats report unexpectedly.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Release note

• fix frequently reconnecting pd client

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• overvenus
• rleungx

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[ti-srebot]

/run-all-tests

[ti-srebot]

@BusyJay please accept the invitation then you can push to the cherry-pick pull requests.
https://github.com/ti-srebot/tikv/invitations

[overvenus]

LGTM

[BusyJay]

/merge

[ti-chi-bot]

@BusyJay: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

If you have any questions about the PR merge process, please refer to pr process.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

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

Commit hash: d2983a9

[ti-chi-bot]

@ti-srebot: Your PR was out of date, I have automatically updated it for you.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

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.