[AIRFLOW-5302] Fix bug in none_skipped Trigger Rule

[kaxil]

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Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-5302

Description

• Here are some details about my PR, including screenshots of any UI changes:
  The task been set none_skipped run immediately even before upstream tasks complete execution.
  Bug:
  

After Fix:
Waits till upstream tasks are complete / skipped and skips if all upstream tasks have skipped

Tests

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  Added

Commits

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  4. Subject uses the imperative mood ("add", not "adding")
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  6. Body explains "what" and "why", not "how"

Documentation

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Code Quality

• Passes flake8

[mik-laj]

Very interesting bug. It made me analyze how exactly the trigger rules work. I once wanted to add tables to documentation that show how trigger rules behave in more cases. I will have to come back to this, because it may be a more interesting topic than it seems at first glance.