dm: fix start task check when both shard-mode and TLS are configured (#11843)

[ti-chi-bot]

This is an automated cherry-pick of #11843

What problem does this PR solve?

When task configuration contains both shard-mode and TLS configuration, start task fails

Issue Number: close #11842

What is changed and how it works?

The content of the task configuration file is replaced with the TLS context populated when TLS configuration exists. The changed configuration file content generates false positives in the pre-checking logic. Reordering the pre-checking and loading of the TLS context can make it work in such cases.

Check List

Tests

• Integration test

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

None

[ti-chi-bot]

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[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

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[sunxiaoguang]

/retest

[sunxiaoguang]

/retest