ddl: fix panic in pause (#47914)

[ti-chi-bot]

This is an automated cherry-pick of #47914

What problem does this PR solve?

Issue Number: close #47902

Problem Summary:
reorgCtx for reorgJob is cleaned up since worker is closed when calling isReorgPaused.

What is changed and how it works?

Use isReorgRunnable to ignore the check.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wjhuang2016, ywqzzy

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-10-23 09:12:55.343177685 +0000 UTC m=+2253172.930287830: ☑️ agreed by ywqzzy.
• 2023-10-23 09:14:27.833358629 +0000 UTC m=+2253265.420468774: ☑️ agreed by wjhuang2016.