Fix the fail start of tiflash because of the zero division when getting cpu number (#9602)

[ti-chi-bot]

This is an automated cherry-pick of #9602

What problem does this PR solve?

Issue Number: close #9212

Problem Summary:

What is changed and how it works?

Check List

Tests

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

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

Fix the that fail to start tiflash because of the zero division when getting cpu number

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-unit-test	6c1a5a1	link	true	/test pull-unit-test
pull-integration-test	6c1a5a1	link	true	/test pull-integration-test

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