tests: use python3 to run http_api test to fix failed integration_tests (#5473)

[ti-chi-bot]

This is an automated cherry-pick of #5473

What problem does this PR solve?

Issue Number: close #5474

What is changed and how it works?

Our CI envs still default to python2 to run tests. http_api requires using requests which brings certifi. Actually certifi's recent releases doesn't support python2 any more.

Release note

None

[ti-chi-bot]

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[zhangyangyu]

/run-all-tests

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-5.3@c6fdb3b). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff                @@
##             release-5.3      #5481   +/-   ##
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  Files                  ?        224           
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  Branches               ?          0           
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  Hits                   ?      13367           
  Misses                 ?       9166           
  Partials               ?       1347           

[Rustin170506]

/merge

[Rustin170506]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: e3dab22

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[nongfushanquan]

/run-all-tests