br: not support executing backup task and restore task at the same time

[hfxsd]

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• This PR is translated from:br: not support executing backup task and restore task at the same time docs-cn#16223
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[hfxsd]

/approve

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[hfxsd]

/approve

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.6: #17077.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.0: #17078.