minor #11963 Unit test fixes
[HttpKernel] Fixing unit test broken since merge 4677e92ffeac80
[Validator] Fixing the way the default time zone is backed up
minor #11963 Fixing unit tests (fejese)

This PR was merged into the 2.6-dev branch.

Discussion
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Fixing unit tests

[Validator] Fixing how default time zone is backed up during testing to not interfere with other tests
[HttpKernel] Fixing merge issue since 4677e92ffeac80

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
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5b3193a minor #11963 Unit test fixes [HttpKernel] Fixing unit test broken since merge 4677e92ffeac80 [Validator] Fixing the way the default time zone is backed up