Only log task state cleanup for configured worker state store backends

[amoghrajesh]

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Noticed this while testing https://cwiki.apache.org/confluence/display/AIRFLOW/Test+cases+AIP103+Task+State+Management with beta1 for 3.3.0, we should only ever be logging Clearing task state from custom backend as clear_on_success is enabled. The database references will be cleared by the API server. when a custom backend is configured AND not when clear_on_success is set on a default backend which could be really confusing when debugging things.

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[phanikumv]

Seeing a CI failure. Replace this line with the below code

with mock.patch(
"airflow.sdk.execution_time.context._get_worker_state_store_backend",return_value=mock_backend),
mock.patch("airflow.sdk.execution_time.task_runner._get_worker_state_store_backend", return_value=mock_backend
):

[Lee-W]

let's add a small unit test for it

[amoghrajesh]

@Lee-W @phanikumv handled your comments, ptal!