pd-ctl: fix the output trim

[JmPotato]

What problem does this PR solve?

Issue Number: ref #4399.

What is changed and how does it work?

Fix the output trim of the pd-ctl command.

Check List

Tests

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

Before:

After:

Release note

None.

[codecov[bot]]

Codecov Report

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

Project coverage is 77.34%. Comparing base (6f8286b) to head (ca7a021).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8309 +/- ## ========================================== - Coverage 77.40% 77.34% -0.06% ========================================== Files 470 470 Lines 61359 61360 +1 ========================================== - Hits 47494 47460 -34 - Misses 10308 10347 +39 + Partials 3557 3553 -4 ``` | [Flag](https://app.codecov.io/gh/tikv/pd/pull/8309/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/tikv/pd/pull/8309/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv) | `77.34% <100.00%> (-0.06%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv#carryforward-flags-in-the-pull-request-comment) to find out more.

[ti-chi-bot[bot]]

@okJiang: adding LGTM is restricted to approvers and reviewers in OWNERS files.

In response to [this](https://github.com/tikv/pd/pull/8309#pullrequestreview-2127737163): > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: HuSharp, okJiang, rleungx

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

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/tikv/pd/blob/master/OWNERS)~~ [HuSharp,rleungx] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-06-19 09:39:39.708698216 +0000 UTC m=+194106.194187044: :ballot_box_with_check: agreed by rleungx.
• 2024-06-19 09:59:51.623313601 +0000 UTC m=+195318.108802431: :ballot_box_with_check: agreed by HuSharp.