patch: fix has_file function to check on every unit instead of only checking the leader

[patriciareinoso]

🏷️ Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Tooling and CI
• Dependencies upgrade or change
• Chores / refactoring

📝 Description

This PR make the function has_file to actually check the given unit instead of checking the leader unit.
This function is used by:

• test_sharded_backups_tls.py -> test_remove_integration
• test_encryption_valid_scenario.py -> test_integration_goes_to_active

which iterate over all the units of the application and call the has_file function

🧪 Manual testing steps

No need, this PR just modifies an check in the integration test

🔬 Automated testing steps

The integration tests using the has_file function still pass

✅ Checklist

• My code follows the code style of this project.
• I have added or updated any relevant documentation.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[Gu1nness]

This change probably means we want to check that all calls to this function provide the leader as unit, but agreed !

[patriciareinoso]

the has_file function is called twice (test_sharded_backups_tls.py and test_encryption_valid_scenario.py)
Both times the test iterates over all the units of the application and called the has_file functions.
So in fact we were checking multiple times that the leader unit has a file , no we check that each unit in the application has a file